Rvpush - broken/change of expected behaviour since 7.7.1

Hi all!

I’ve spent some time debugging some crashes that we’re having at my studio when using some old mel code that spawns an rvpush process. These lines are the minimum working example to reproduce a crash:

int $fps = 25;
string $filesOut = "/usr/tmp/blastj2YPAT.*.tif";
string $playCmd = "rvpush -tag playblast merge [ -fps " + $fps + " " + $filesOut + " ] &";
python("import subprocess; import os; subprocess.call( '" + $playCmd + " ', shell=True, env=os.environ)");

The first execution of this code runs fine. Re-running it a second time causes rv to fail to parse the command line arguments, basically it appears to interpret each whitespace separated token as a different file to read.
I’ve tested with rv 7.6.0, 7.7.1 and 7.8.0 with the same exact code and 7.6.0 still works as expected.

Here’s a screengrab of the Inputs section in RV:
Screenshot 2020-12-02 at 16.05.45

Has anyone experienced the same behaviour? I couldn’t find anything on the release notes.
I though of posting here before opening an official ticket in case it’s useful for someone else.