America's Biggest Video Games Union Goes on Strike over Microsoft Outsourcing

When would be the wisest timing?

In my experience, there will always be nay-sayers complaining about the timing, no matter the circumstances. Unions are rarely needed when things are going well.

It seems that going on strike because the employer does not fulfill its contract is a good time to go on strike.

If management has any ability to make something a flop - and it surely does - then your timing argument gives management carte blanche to break union contracts by deliberate mismanagement, set thing up for a flop, and use that as the excuse for union breaking.