I have also been getting a number of fatal Houdini crashes when using the Octane IPR (Octane 2020.1.0.8 / Houdini 18.0.460). I haven't compared it to MPlay, but it's fairly easy to get it to crash particularly when trying to reload the IPR. In the attached crash report (octane-01.log) I attempted to reload the IPR after making an adjustment to the displacement height on a material as it was not responding.
Attempting to close the IPR when it's calculating also crashes it at times. In this instance I turned off Render Region and then a few seconds later attempted to close the IPR 'octane-02.log'.
Ironically I was able to get Houdini to crash multiple times trying to add a light while the IPR was open. I would then position and scale the light and hit Reload on the IPR to have it show the newly created light. I was able to reproduce it 3 times in a row, but wasn't able to get a report (The path in the Octane debug dialog was pointing to a non existent folder). As soon as I set the Octane debug logging in the settings to output to the console I couldn't get the IPR to crash, ironically..
I've also managed to get a crash trying to update point colors on my model while the IPR was open. Houdini subsequently attempted to recalculate some VDB nodes down the line and then crashed, however I wasn't able to record a log for that session. I'll keep trying to collect bug reports as I experience the crashes. Let me know if I can provide any further info to help out.
Best / Travis
win 10 / i7-8700K / Nvidia 2080 Ti / Quadro P2000 / DDR4-3200 64Gb