@LarryRuane wrote a test which set activation heights for overwinter and sapling. The test passed but failed on master, so we bisected to find a problem with 40b9527.

The issue is that regtest mode cannot rely on release height, so the Sapling branch id was being selected instead of Overwinter when signing an Overwinter tx.

chainHeight = 377000
...chainActive.Height() + 1 = 202
...APPROX_RELEASE_HEIGHT = 377000
consensusBranchId = 76b809bb
Assertion failed: expected: <success> but was: <failed>

whereas the expected output is:

chainHeight = 202
...chainActive.Height() + 1 = 202
...APPROX_RELEASE_HEIGHT = 377000
consensusBranchId = 5ba81b19