That's not what you wrote in the issue description. You wrote, formatted to (presumably) represent verbatim input:
H 0 * * * OR H 7 * * * OR H 14 * * *
And that is not valid.
Please explain what you're doing, in detail (i.e. full step-by-step instructions what you're configuring). Try to find out what conditions need to be met for this to not work. Is it only when you use 'H'? Is it only if the 'H' is on the 'minutes' field? Etc.
Set up a log recorder for the logger hudson.triggers.SCMTrigger as described on https://wiki.jenkins-ci.org/display/JENKINS/Logging and report its output.
This is not a valid polling schedule.
Has nothing to do with the Poll SCM Plugin.