NB: This is resolved. See answer below.

I've had some work done at home recently that's required external sealing around windows. That was done two weeks ago, the painter painted over the filler, but now the paint is cracked. The windows that have only been primed are not cracked. There is the suggestion that the sealing around the window was done with two different products, which could explain this, but seems a little too convenient.

The painter is saying the sealer cracked. The window company is saying the paint has cracked. I can't say for sure. If it's caused by the sealer the window company used the painting company shouldn't have to pay to repaint. If it's just cracked paint the window company shouldn't have to do anything. Note that neither have been fully paid.

The window guy is saying they use Bostik silicone sealer, which is great quality and should never crack. The painter is saying he's seen cracking before where no more gaps was used instead of silicone. I don't know if we just need to silicone over the cracks and repaint, or if we have to remove all the seal and do it again. My concern is it will happen again in weeks or months and it'll be difficult to get either company back.

Can anyone give me any information or suggestions how to progress?

NB: I'm deliberately not mentioning company names and would appreciate if this discussion is about the issue, not the parties involved.

NB2: speculating about the cause of the problem, while interesting, isn't useful. I really need to find someone authoratative to come in, assess, and decide on a resolution. I guess Dulux or Bostik are the obvious choice. I'll ask a friend who works at Dulux.