I have several importers in my site, which is set to run "as often as possible". When cron is executed, some of them seems to be updating every item even though nothing has changed. If I run the importers manually from the standalone form, everything works as intended, returning "There are no new nodes".
I've traced this down to the hash check, in
FeedsProcessor::process(). The stored hash is loaded as it should, but the hash for the current item is being calculated differently. It seems as this is due to a static variable in
FeedsProcessor::hash(), which stores the serialized mappings. I think that the static variable is getting it's initial value based on the importer that is triggered at first. The rest of the importers, will then use that static variable.
I haven't done any thorough research, but I've removed the static variable to test my thoughts, and everything is indeed working as it should.