Steps to reproduce:

1. Open Monitoring > Problems.
2. Use the new customizable table feature in a filter tab (column width was changed, probably by dragging a column edge; the saved layout contains "time" column width of 400px with overrides).
3. Reload the page.

Result:
The Problems table is rendered broken: each cell of a row (checkbox, time, severity, recovery time, status, info, host, problem, duration, update, actions, tags) is displayed on its own line, one under another, instead of as a table row. The table header, including the Customize table button, is not usable, so the layout cannot be reset from the UI.
Other tables (Monitoring > Hosts, Latest data) render correctly. No JavaScript errors in the browser console (only accessibility warnings about label for).

Expected:

• The table renders correctly for any saved column layout, or an invalid layout is ignored or reset automatically.
• Reset layout stays reachable even if the table cannot be rendered.

Workaround:
Delete the saved layout from the user profile and log in again:
 
sql
DELETE FROM profiles WHERE userid=<userid> AND idx='web.monitoring.problem.datatable';
After this the table renders correctly again.

Additional info:
Saved profile values (profiles.idx = 'web.monitoring.problem.datatable'), anonymized:
 
{{idx2=0: <paste anonymized value_str>
idx2=1: <paste anonymized value_str>}}
Problem names in the list were long (log-based triggers with ~200–300 character event names). It is not confirmed whether this contributes.