Philippe,
I have a feeling that a chunk of the epoxy (or something else that failed to bond properly) may have separated, is floating & is blocking the feeder tube once suction is present.(also, is your fuel filter at the tank or the fuel pump?)
I had a similar problem with my '53 Buick years ago...the original tank had a lot of 'floaters' in it, causing the engine to stumble. Once I connected a hose between a jerri-can & the fuel pump at the engine, the car ran beautifully! (I replaced that tank altogether)
Carl Falletta
'67 Crown Coupe (ylw/blk)
Las Vegas NV USA