I bought the enlarger second-hand. It's my first, so be gentle with me. No instructions came with it, nor with the medium format conversion kit that I bought new from B&H. Beseler ignores all emails and there is no manual online on their website. I will doublecheck everything I can when I am home tonight. No idea how to "align" the enlarger. It seems fairly well lined up to me, but I don't know what I'm doing. I'll check the lens... I know I have a 50 and an 80. One is a Beseler and the other a Rodenstock. They both seem capable of sharp prints up to 11x14
Oh - the actual problem seems to reoccur in just one corner. It's not getting enough light on that spot, which happens to be the righthand corner closest to the enlarger.