Actually I am having the exact same problem but need to solve it.I checked my appdsscript.json and it is set correctly as well. I am using:

var details=[[events[i].getStartTime(), events[i].getTitle(), events[i].getStartTime(), events[i].getEndTime(), events[i].getDescription()]];

The time is one hour off once the dates hit the time change in April. however, to test I did this (ADDED A +1 TO MY getStartTime and Get EndTime):

var details=[[events[i].getStartTime(), events[i].getTitle(), events[i].getStartTime()+1, events[i].getEndTime()+1, events[i].getDescription()]];

I knew it would kind of blow up but what is displayed in my spreadsheet was interesting. This is what was in the cell:

Fri Jun 13 2025 18:00:00 GMT-0500 (Central Daylight Time)1

The time is actually correct! It dropped to GMT-5 instead of GMT-6. Is my problem in Google Sheets?