Error 500 after upgrade to v2026.9.0 / temporary solved by clearing browser data

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1

Hello,

We have a discourse for the Scala PL for users which was running fine for years :

Last week, I upgraded to the latest version using "./launcher rebuild app
", since then we have very often the error “Oops - Error 500”. It appears when the website was already visited. In a browser private window, it works fine. So clearing the website data on the browser works for some time, but the problem appears again.
I tried to update 2 times discourse for the dashboard, then also to rebuild it again using “./launcher rebuild app”, but it’s still the same.
In log/rails/production.log I only see:
Started GET "/" for 127.0.0.1 at 2026-09-03 09:57:56 +0000
Processing by ListController#latest as HTML
Rendered layout layouts/application.html.erb (Duration: 391.6ms | GC: 229.5ms)
Completed 500 Internal Server Error in 474ms (Views: 392.5ms | ActiveRecord: 0.0ms (0 queries, 0 cached) | GC: 236.0ms)

Any idea what’s wrong and what I could do to solve the problem?
Thanks a lot!

Fabien

2

Looking deeper, deleting the _t cookie remove the “error 500”, but the error appears again when logged after maybe around 1h.

3

v2026.9.0 has not been release yet - are you referring to the development/latest version?

4

I’ve not set any specific version, so I guess by default it should be latest (according to "tests-passed" is now "latest" ).
In the dashboard, this is the version I get at the bottom.

5

In /logs, can you find the 500 error and share the error and its backtrace?