Scenario. A and B are contracts, A has verify method. In this verify method A calls B and B also calls A. We use A to verify some transaction, so upon running the verification script we get an evaluation stack that looks like this (invocation script not included): A¹ -> B -> A². With this change if A² is to call GetInvocationCounter the result would depend on whether A¹ called GetInvocationCounter or not, it could either be 1 or 2.

What I was thinking more wrt this bug is initializing invocationCounter before A¹ is run (in LoadScript probably).

Please, take a look @roman-khimov

LoadContext part seems to be fine (but maybe all of CallContractInternal logic related to invocationCount could be moved there?), not sure we need to change GetInvocationCounter.