I've investigated this effect in my pool and here's the explanation: I found out that condor assigns some arbitrary "NEGOTIATOR_PRE_JOB_RANK" to my machines which overwrites the "Rank" _expression_ in the job's submit file. As I've defined NEGOTIATOR_PRE_JOB_RANK neither in my global condor_config file nor in my condor_config.local file it's unclear to me where this comes from. Definitely, there has been a change from condor 8.0.5 to condor 8.2.4 in this regard such that an erroneous (?) value for the NEGOTIATOR_PRE_JOB_RANK is created if it's not defined in the condor_config file. For my case the solution was simply to set
NEGOTIATOR_PRE_JOB_RANK = 0
in my condor_config.local file.