Some contracts require 66% or 75% of votes to be able to change the repartition of shares or extend capital, or even any shareholder can veto. Some contracts don’t have conditions.

Philosophically, even if not written in the contract, someone could convince you to dilute at the last minute. The best interest of a buyer is to put the target in close bankruptcy before buying it. Anything is possible in peer-to-peer negotiations, and legal framework can only go so far.

That can't be evaluated without full knowledge of the contract and a lot of knowledge of the personalities involved. There is no 'safety' in dealing with other people, you need to know whom to trust.