Had a porous casting in a DT100 cylinder from new that leaked fuel mix through the side of the left transfer low down near the base.
Be the last thing i'd expect on yours though.
If it a less than perfect case mouth or cylinder base you could make a gasket out of thicker gasket material.
I did that on my 490 but because it kept sucking the gasket in around the transfers.
Went to the local auto parts shop & asked if gasket paper was still "a thing". She said hang about, we have two rolls of different gauge thickness we'd like to clear as no-one buys that nowdays.
So i bought them for a song almost.
Think they are of 0.8mm & 1.6mm but i used the thicker one in my case & worked perfect.
Left it overlapping the edge by a little using 'my theory' that it'd squash down & leave a fractional ledge to eliminate the chance of sucking in.
Sorry, most of that info isn't any help in your case.