Scoring goals has been a problem for Albion all season but they have defended reasonably well for much of the campaign.
Now a pattern is developing of giving away bad goals, which, together with failing to take chances, is a recipe for certain relegation.
Crewe's winner, Norwich's opener and both of Leicester's goals at Withdean are all recent examples of Albion presenting the opposition with an advantage.
The goal which stretched the losing sequence to six at Home Park was a comedy of errors and highlighted an all-too familiar pattern.
I have given up counting the number of games in which Albion have been the better side, fail to find the net, fall behind and then, once adrift, do not look like retrieving a result.
They should have been at least 1-0 up when, in the 37th minute of a scrappy game, Lilian Nalis exploited terrible defending to score his first goal for Plymouth since joining them on a short-term contract from Sheffield United.
It started from a long throw-in, illustrating a growing vulnerability from set pieces.
Dean Hammond, recalled to the starting line-up at the expense of Kerry Mayo, attempted to clear but succeeded only in lifting the ball back towards his own goal.
Wayne Henderson advanced off his line and tried to punch away the danger over a cluster of bodies.
Nalis said thanks very much, the long-haired French midfielder's lob from ten yards finding the vacant net.
It was a farcical way to lose and Albion must stop making individual mistakes at the back to retain any hope of avoiding the drop. They have now kept only one clean sheet since Boxing Day.
Manager Mark McGhee said: "I will need to look at it again. I would say on this occasion Wayne was at fault. I think he came for a ball that he couldn't get.
"His enthusiasm overcame his brain and he came over too many bodies. Unfortunately it dropped to one of them instead of one of us and we ended up losing a game we didn't have to lose, certainly not in that situation."
The goal Albion conceded is only half of the story. The goal (or goals) they failed to score beforehand, when they were well on top, proved just as costly.
Young Joe Gatting was the main culprit this time. He marred another encouraging contribution as a target man by spurning the kind of opportunity he gobbles up regularly for the youth team and in the reserves.
Gatting had already forced Plymouth's French keeper Romain Larrieu into a fine stop when he shinned Adam El-Abd's cross goalwards as he was challenged by Anthony Barness.
Then, in the ninth minute, came a gilt-edged chance to claim his first senior goal.
Gatting instigated the move himself, neatly finding Seb Carole near the halfway line before making an intelligent run through the middle.
Carole, back in for the suspended Gary Hart, released him with a raking, diagonal pass but Gatting scuffed his left-foot shot well wide from ten yards out.
McGhee said: "Joe played well again and showed he is ready for this level but he has still got to take that next step into being a goalscorer for us. There were chances which should have resulted in goals, regardless of his age.
"I said to the players before the game, watching Football Focus and seeing Tottenham with Jenas and all of their young players, they are just the same age as our boys.
"If you are good enough you are old enough and if you are good enough you should be putting the ball in the back of the net when chances like that arrive.
"I think I'm quite entitled to, of course, praise them for the all-round performance but to be critical that they have not scored a goal."
Missing chances is not the only reason why Albion have failed to score in five of the last seven matches. They also sometimes do not react quickly enough and get enough bodies into the box when openings are made.
There was a classic example of this in the first half on Saturday, when Hammond put Alex Frutos away as Plymouth looked in vain for offside. He pulled the ball back but there was nobody there to capitalise.
The second half, when the wind was against Albion, emphasised how difficult it can be once you have fallen behind to a side managed by Tony Pulis. His teams are never pretty to watch but they are pretty effective.
Plymouth were content to keep their lead, rather than chasing a second goal, and never looked like relinquishing it. A fourth home win out of five was comfortably secured after the break.
"In the first half we absolutely battered them," McGhee said. "We bossed the game. To lose a goal from a long throw was tragic and I cannot believe we lost to a goal like that.
"In the first half we were excellent. In the second half conditions made it a little bit more difficult to get out and put any sort of real pressure on them. It's another game we have come away from wondering how we conspired to lose it."
As Hammond pointed out, Albion are fortunate in one sense. Sheffield Wednesday's poor form is just about keeping their hopes alive. Otherwise they could be dead and buried by now.
All the while the safety gap stays at five points there is a chance. If it increases, even by one point, then the mountain will become a cliff-face.
The trouble is at the moment it is hard to see where the Seagulls' next point is coming from, yet alone a win.
- Albion (4-4-2): Henderson 6; El-Abd 7, Hinshelwood 7, Butters 7, Lynch 7; Carole 7, Carpenter 7, Hammond 6, Frutos 6; Kazim-Richards 7, Gatting 6. Subs: Mayo for Frutos (withdrawn 63), McPhee for Gatting (withdrawn 80), Reid, Nicolas, Martin.
- Plymouth (4-4-2): Larrieu; Barness, Doumbe, Aljofree, Capaldi; Norris, Wotton, Nalis, Hodges; Pericard, Chadwick. Subs: Evans for Chadwick (withdrawn 66), Buzsaky, McCormick, Zebroski, Djordjic.
- Matchfacts
- - Shots on goal: Albion 1 Plymouth 4.
- Shots off goal: Albion 4 Plymouth 5.
- Corners: Albion 0 Plymouth 6.
- Offside: Albion 0 Plymouth 2.
- Free-kicks Albion 17 Plymouth 20.
- Albion bookings: Hammond (45) foul, El-Abd (75) unsporting behaviour, Hinshelwood (77) foul, Butters (87) foul.
- Plymouth bookings: None
- Albion scorers: None
- Plymouth scorer: Nails (37)
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