As others have mentioned now, the implementation Exact uses is flawed (assuming that they're strictly using pushes).
Exact shouldn't purely rely on pushes from bunq for transaction handling. It is well known that only using such an implementation is unreliable, or at least, can't be considered as consistent, which counts for any service providing push endpoints. They've to implement a method for querying and syncing transactions as well for scheduled checks.
I'd recommed to communicate this to Exact through your support emails, possibly along with a link to this thread.
I must note that missing so many transactions when purely relying on pushes is worrying, but I don't think that can't be categorized as the real problem here. Their (meaning Exact) method for registering transactions should be improved to ensure consistency.