Can a normal DML operation cause a CTXCAT index to get "FAILED"?

we have some Oracle Text indexes built using "INDEXTYPE IS CTXSYS.CTXCAT".

Every now and then they go into an invalid state (all_indexes.domidx_opstatus is 'FAILED' for them) producing an "ORA-29861: domain index is marked LOADING/FAILED/UNUSABLE" error when doing DML against the table.

We (yet) weren't able to find the reason for this.

Dropping and re-creating the indexes solves the problem, but I would like to understand what causes this.

My understanding is that this should only happen when the "CREATE INDEX" has been interrupted somehow (shutdown abort, statement fails due to resource problems) or concurrent sessions tried to rebuild the index.

Are there any other situations when a CTXCAT index can go into an invalid state (namely any DML operations?) Or something else I need to inspect in the application code?

Regards
Thomas

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