Developer 1 fetches code, changes flag A. Rebuilds config. Developer 2 fetches code, changes flag B. Rebuilds config. Developer 1 deploys built config. Developer 2 deploys built config, inadvertently reverts developer 1's changes.
Imagine the first eng team did a forward movement revert that corrected the issue and had a new head bits that gets deployed, where shortly after another eng fires off the second process type and tells the system to pull back to the last revision (which is now the bad revision as it was just replaced with fresher deploy bits).
Having two revert processes in the toolkit and maybe a few disperse teams working to revert the issue without tight communication leads to this issue.
I think this is more likely the basis issue vs a bad merge (I assume that the root cause was broadcasted wide and large to anyone making a merge)