Not as far as I know although there are several different designs of
these seals, the cheaper ones, for example the ones made from clear
plastic, are difficult to get a decent seal. I assume this is a
low-level cistern (as opposed to close-coupled) and you mean where the
flush pipe connects to the pan and not the cistern? The seal where the
flush pipe connects to the CISTERN should have no flexibility in it all
and it should not be difficult to achieve a good seal.

You could try getting a new seal and seeing if it makes any difference
(it may well do, if you buy one of the more substantial variants).
However if this fails you are left with two choices (a) Realign the
pan/cistern properly or (b) Dry the whole thing off and bodge it by
running a bead of silicone around the leak. This should hold because
the leak is under a low pressure but, as I say, it's a bodge.

Luke