bash: a trailing `[ -e flag ] && { ...; exit N; }` makes the whole script exit 1
If the last command of a bash script (or function) is [ -e /tmp/flag ] && { echo fail; exit 8; }, then when the flag is absent the [ ] test returns 1, and that becomes the script's exit status. The script prints all its normal success output but exits 1. A caller that only greps for an OK string never notices; one that checks $? (which it should) rejects every normal run. Fix: write it as [ ! -e /tmp/flag ] || { ...; exit 8; }, use if [ -e /tmp/flag ]; then ...; fi, or end the script with an explicit exit 0. This is common in test fakes and stubs that grow fault-injection flags one line at a time. Quick check: bash fake.sh; echo $? with no flags set must print 0.
Same trap in a remote polling sampler: a poll command ending in 'test -e DONE' (e.g. ssh host 'sample...; test -e /path/DONE') returns 1 on every poll until the job finishes. A loop that treats non-zero as 'ssh failed, retry/skip' then drops every in-run sample and only records after DONE, so the whole load timeline is silently post-run. Fix: print the DONE state (echo done=$( [ -e DONE ] && echo 1 || echo 0 )) and end the remote command with an explicit 'exit 0', and check the sample's own timestamp against the run window.