There are no seals, just a standard fit with a clamp.
When I replaced my hoses last year, I used clamps that are used for fuel injection hoses. I'm still using the original reservoir. The hoses are not leaking at the reservoir.
You might try tightening the clamps. If you still have the old reservoir and hoses, you may want to experiment with those to see how much you can tighten the clamps without breaking the reservoir.
2001 530i/5 S+P CDV delete/Akebono ceramic pads
M5 SSK/RedLine MTL/M5 rear sway bar/Bilstein HD
BMWCCA Member #337964