Great explanation! Thanks :)
From the error it looks like you need to flush the cache. Are you using minfication? If yes, you might want to disable that and enable later. Also looks like the Layer Slider editor gets called. Are you using Layer Slider here?
I checked your site and I can see that both Enfold theme and Optimizepress is activated with no issues when I tried to follow your instructions above. Can you tell us more how you disabled the theme from loading? as you have mentioned and also tell us how we can see the error back?
I have tried what you mentioned, and noticed that it was css that was checked (disabled), I tried to uncheck it and do your instructions here: -update-stops-optimizepress-from-working/#post-800405 and it does load properly on my end. Screenshots in private content.
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