CF 6.0.27 Read Data fails when table columns were dropped

Hi,
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today i deleted some unused database columns in my cf_data table which are not filled or read anymore.
Now i get the error that a field is missing which i deleted previously.
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What i've done so far:

1. I checked all my existing elements for that field and didn't find an existing configuration which uses that column.
2. I backed up my form and had a look into the backup file for that column - nothing.
3. I made an "update table" refresh in dbread and dbsave elements - no change in behaviour

Any suggestions?
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Thanks in advance,
Stefan

Thanks, that helped!