Hello !
You told us that this enlarger has been used for many years.
Have you considered the fact that the head guidance system on the column could have suffered and, giving more play than planned, allow the head to bend towards you, thus destroying alignment. Also, the negative carrier path may be worn and also be "less square" than it should.
I do not know the construction of the LPL, but as LPL is a reputable make of high quality enlargers, you should be able to correct the play and/or replace the worn guidance pads to restore a proper operation...
This is, of course, only a theory, as I do not know your enlarger but IMHO is worth a check.
You've a fine piece of gear so worth a refurbishing !