Different builds from the same commit

Given two runs from the same commits, I get two different outputs.
First one:
http://autumn.ocamllabs.io:8081/job/2023-07-04/144707-ocluster-build-5c0271
Second one (run via "rebuild" button):
http://autumn.ocamllabs.io:8081/job/2023-07-04/155012-ocluster-build-8ac42b

Any idea on what is the reason for lack of reproducibility?