Grohe Cistern issue

I have a couple of concealed slimline cisterns.
They have started to leak water into WC, this is 100% not down the overflow pipe, as water level is well below that.
Took it out cleaned all … still the same (or worse if anything) …. From empty the infill ‘torbeck type’ starts filling, all is fine until around 50mm deep .. and the water starts to leak …. Assuming that the bottom ‘main seal’ is OK, as nothing gets past that initially, only leaks when it get in over the float, so my logic is that is must be getting past the inner seal.

Are these spares items ?
The main seal aprox 66 OD and 48 ID has No. 14.11.29 1 DAL
The inner seal aprox 48 OD and 30 ID has No. 14.11.30 8 DAL

Picture shows siphon, and the seals in the lower picture.

There may be tiny "blebs" in the seal, almost like little bubbles you can buy replacement seals or the whole cartrdge from toiletspares.co.uk

Yep ..both seals have what look like Blisters.
I'll try 'toiletspares' thanks

I know this was a while ago but my comments might help others - had a problem with weeping Grohe cistern and cleaned the seals and removed any limescale I could find, ensured it was smooth but still wept. Having decided to get a new DAL piston for about £10 but they out of stock. Had another look and found that the weight of the piston could be increased by putting some lead weight round the central shaft (had some for our fish tank fortunately). This seems to have done the job for now as the seal is now pushing down more of the flow pipe thereby sealing any gaps which was letting the water through. Why Grohe don't make the piston heavier in the first place is of course an issue - probably because they get repeat business from us buying replacements or the seals themselves which are about £4