I have configurations with "Next Build Version" defined as
Use specified version
Version ${vars.get("verMajor")}.${vars.get("verMinor")}.${vars.get("verRelease")}.${vars.get("verBuild").increase()}
and appropriate variables ("verMajor", "verMinor", "verRelease" and "verBuild") are set.

I can make a build request via API. In that request I can redefine variables used for the build.
When I redefine "verMajor", "verMinor" or "verRelease", build version uses this change and it's ok. The appropriate configuration variables are not changed and the next build versions are calculated with the values if there was no any redefinition (and it's ok).
But if I define "verBuild" variable in a build request, it's value is"remembered" (configuration variable stores this values) and the next builds use this redefined value.

E.g. in the beginning I have configuration variables defined as
 verMajor=1, verMinor=2, verRelease=3 verBuild=4
First build is 1.2.3.4
Then I run API build request with redefined verMajor=7, so, the second build is v7.2.3.5 (verMajor is redefined, verBuild is increased, others are not changed)
Then I run API build request with redefined verMinor=5, so, the third build is v1.5.3.6 (verMinor is redefined, verBuild is increased, others are not changed)
The same for verRelease=4, so, the fourth build is v1.2.4.7 (verRelease is redefined, verBuild is increased, others are not changed)
Then, finally, I redefine verBuild=1, fifth build is v1.2.3.1,
And then I run sixth build without any redefinition, and it's version is v1.2.3.2, so, seventh will be v1.2.3.3, eightth will be v1.2.3.4, and so on