Regular Expression Replace - hanging in Flow

Is there an issue with the Regular Expression Replace action?

I have a flow that cycles through an array (using for each loop) then replaces some text in a variable, updates the variable then moves on to the next step in the loop.

For some reason it works once, then hangs the next run, then works on the next run and hangs again on the subsequent run.

This is the part of the flow that's hanging...

If I cancel this flow, then resubmit it, it runs just fine, finishing the entire flow in under a minute.

I let it run this time, finished after 30m. The 2nd and 3rd replace action during the first loop took 8m and 22m respectively. All other replace actions during the 2nd and 3rd loop finished in seconds.