Issue is known to Symantec.
Solution for 7.1 environment is included in 7.1 SP2 MP1.1 Rollup v10.
Solution for 7.5 environment is included in 7.5 SP1
1) Reinstall affected software to add back missing registry value
2) Prepare separate script for the same operation, which maybe then deployed to clients
3) Install back AM plugin.
Issue was reproduced on 7.1.2 MP1 with Rollups up to v9 and on 7.5