Read the statement by Michael Teeuw here.
MMM-CalendarExt3 only one calendar not updating
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 Something even stranger - if I immediately refresh the page it also works. Here I mean is: npm run server
 got to browser and bring up host:8080
 calendar will say “Loading” for a very long time
 (despite the events getting broadcast)But if I : 
 npm run server
 go to browser and bring up host:8080
 calender says “Loading”
 Refresh the page immediately
 calendar says “Loading”
 calendar will immediately show the events as soon as the events are broadcast
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 @emlowe oh, “cool” ugh, i opened an issue about that last year just reopened 
 https://github.com/MagicMirrorOrg/MagicMirror/issues/3380can you add the contents of your post in an comment 
 actually this one
 https://forum.magicmirror.builders/topic/19345/mmm-calendarext3-only-one-calendar-not-updating/30?page=3#
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 Hmmm… I was in our traditional ceremony with my family - a lunar new year, so I couldn’t catch this post. Sorry. 
 Anyway, this symptom is not my module’s fault, right? There were some reports similar to this, but not figured out.
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 @emlowe can you try this , configure bigger socketio buffer 
 see the post in the issue
 https://github.com/MagicMirrorOrg/MagicMirror/issues/3380#issuecomment-2645778523
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 ok, that didnt help 

