When testing TiddlyWiki 5.3.7 with the Autocomplete plugin, it seems that opening a tiddler in a new window triggers the red window of death. This issue does not occur with TiddlyWiki 5.3.6.
@Maurycy
I’m not sure what changes in TiddlyWiki 5.3.7 might be causing this issue. With a bugfix for 5.3.7 about to be released, it might be worth checking it out.
Maurycy is taking a look right now 
Edit 1: Once I added support for 5.3.7 to my automated tests for the plugin it detected the error, yay for tests! Now to figure it out.
Edit 2: The issue was caused by this change to the core → adding support for registering multiple listeners for a widget event. Fix incoming today!
That’s a problem of the autocomplete plugin.
The tw-com version does not have a problem. This RSOD typically points to problems for un-initialized variables. Mainly when configuration or status tiddlers are missing.
I think it’s reasonable to accept translation updates at this point, so I have merged @Maurycy’s update to the Polish translation.
Resolved quickly in an update. Thanks, @Maurycy, for your swift action.
@jeremyruston This small fix is ready for v5.3.8.
As well as other ones that I mentioned before:
Yes! How dare you let TW deadlines slip due to being ill! 
But seriously, hope you’re ok and TW can always wait.
Since v5.3.8 hasn’t been released, I think this small fix can be included in v5.3.8.
Updates since my last post:
I now plan to make the release on Thursday 7th August, and have updated the OP to reflect the revised timetable.
Pinned till 7th Aug. 2025 - 12:00 GMT
