Not many are mentioning that they signed to say no more legals going forward from them.
With this you really have to see exactly what was agreed to. With a lot of legal stuff it's all about one-upmanship in how carefully you word the document (basically creating loopholes)
So while we're talking about moving goalposts etc, chances are that in fact both sides were using completely different goalposts and the change in wording is Wasps saying "we didn't mean those goalposts, we meant these" or SISU saying "we don't consider this to be legal action". The change in wording is reflecting their original intention, which they realised what SISU had signed up to didn't do. Basically SISU got one over them and when they realised they said "we're not having that" and wanted the agreement rewritten more carefully to encompass what they actually meant.
I was playing pool once with a mate and was completely snookered and he said "if you pot anything here I'll give you a fiver", so I turned around and potted one of his balls over a pocket and demanded a fiver. He never said I had to pot one of my balls......
Wasps may have meant originally they wanted all legal action regarding the Ricoh to stop and none more to be begun. SISU agreed they would stop all legal action against Wasps, which isn't the same thing. Wasps legal representatives should've spotted this, but didn't and when they did they wanted the document rewritten. It all adds to the animosity and distrust and at that point talks were almost certainly irretrievable.
Some would see it as Wasps moving the goalposts and reneging, others would see it as SISU deliberately not playing in the spirit of the game.