nsAppShell:EventWindow error with latest builds of Serpent 52

I have already mentioned a long time ago that I'm ocasionally met with an "exception breakpoint" application error for basilisk.exe when Serpent 52 is getting sluggish and I try to restart the browser. But in recent builds, this error message is preceded by another error message:

nsAppShell:EventWindow: basilisk.exe - Application Error
The exception Breakpoint
A breakpoint has been reached.
(0x80000003) occurred in the application at location 0x1000fba6.

Click on OK to terminate the program
Click on CANCEL to debug the program

A similar (same?) problem was previously reported by @XPerceniol back in December 2021:

https://msfn.org/board/topic/182647-my-browser-builds-part-3/page/74/#comment-1209106

I kept returning to build 20260117 because of this. Since I don't update Serpent frequently, the first version I know that exhibits this problem for me is build 20260228. The most recent build I have tried is 20260815.

To pinpoint the exact version the nsAppShell:EventWindow error starts to appear, I have been running build 20260131 for over a week and it hasn't crashed with the nsAppShell error. Next, I will try builds 20260214 and 20260221.

The changelogs for builds 20260214, 20260221 and 20260228 don't show anything obvious that might cause this for me, but I admit I don't understand some of the entries.