Several crew members with BOTH 'uncredited' and 'credit only' for same job?

While having both attributes is certainly inconsistent and needs to be fixed, looking at the credits is the only way to be sure which is wrong. While (credit only) is rare for movies it is not impossible although in some cases (scenes deleted), which implies (credit only) may be more appropriate. Note that the help for (credit only) says "this is most common for a TV series" which clearly implies that it can and should be used on non-episode credits where appropriate.

A Thanks In Memoriam credit does not, in my opinion, need (credit only) as well despite that being quite likely.

Note that when you look in the update form there are two different credits, one with "credit only" and one with "uncredited". So a software fix would have to account for this.

Thank you for noting this.  I tried to see if this had been discussed before and (obviously) wasn't sharp enough to locate that topic thread you linked to.  Sadly, there are now even more titles that have the problem than the ones listed in that topic so evidently IMDb is allowing even more of these anomalies to be created.

I corrected a handful of incorrect 'credit only' attributes for the title on which I first noticed this problem because I carefully looked through the entire credits and those people had no credits at all in the film so somebody had messed up and entered 'credit only' instead of 'uncredited'. 

It seems extremely easy to block the system from accepting a credit with both 'credit only' and 'uncredited'.  I cannot imagine it being a difficult piece of programming.  It looks like they simply don't care enough.  Disappointing.

As Peter said, the problem is that there are two credits, one with each attribute. The examples are also all crew credits with an occupation in addition to the more general heading. There are a lot of changes that can lead to this situation. Name or title merges with one credit from each, correction of the occupation where what were two occupations becomes one and probably others too.

Preventing the addition of new instances of this problem caused by a new credit submission is probably fairly straightforward and may be in place already. Preventing the situation arising as a side effect of some other change is harder, not least because there is no obvious way to pick one or the other when the conflict is detected. What if one contribution was supported by evidence that a person did the job to (uncredited) and the other by a screenshot of the credits with a claim that the person did not actually do the work (credit only). The correct credit might be with neither attribute so you cannot just delete one or the other.

As Owen mentioned there are a number of routes that can lead to an inconsistency like this. The pairing of these attributes is clearly invalid and while we do very much care about the quality and consistency of all data on the site, sometimes errors like this get through.

To be honest it is very hard for Data Editors to verify these when there is conflicting information. If we cannot verify, is it better that we reject the credit(s) or that we approve them and hope that our faithful contributors, like yourselves, can assist in verifying and correcting them? Unfortunately we simply do not have the resource to audit and verify every data inconsistency.

We have an open issue for this on our backlog but it is unlikely to be prioritised over other higher impact improvements. It would be great if you could fix them were possible. Im sorry I dont have a better answer