Rigged up my 'new' Devere 504 enlarger tonight after some prelim maintenance.

I placed a neg in the 5x4 holder and projected onto the baseboard and noticed a series of fient but noticable concentric square rings around the image. Further investigation determined that it was flare from the bellows. Is this normal. I have used an LPL enlarger but did not notice this problem.

Would it be worth painting the inside of the bellows or what else can you recommend.