>>>>>>>Deleted record was the solution.
>>>>>>>Late coworker had added a place to delete records I've never thought off.
>>>>>>>
>>>>>>>Customer seems to use this on regular base, but normaly the garbage collection catches the problem.
>>>>>>>
>>>>>>>(>ლ)
>>>>>>
>>>>>>An index on !deleted() may help
>>>>>>

>>>>>>index ..... for !deleted() 
>>>>>>

>>>>>
>>>>>Changing tableupdate(0, to tableupdate(.T., solved it an instance without touching the index. It was very simple. :) I will keep the FOR clause of INDEX in mind, anyway.
>>>>
>>>>INDEX... for disables Rushmore optimization
>>>
>>>I don't think so, Bill
>>>
>>>Help reads
>>>

>>>When Visual FoxPro can determine that a query should not return deleted or undeleted records, and if no unfiltered index is present, it uses INDEX ON <expression> ... FOR DELETED() or INDEX ON <expression> FOR NOT(DELETED()). 
>>>
>>>For example, the following queries are now optimized:
>>>

>>
>>That's a surprise, Gregory.
>>I've always thought that any filter on the index would disable optimization.
>
>It used to be - I had two indexes in vfp6 -
>
>Think the deleted() optimization was introduced in vfp9
OK that makes sense.
My experience was with earlier versions
Thank you for that information.