I supply to them. And they had some mid prized sales. Unfortunately not too often - then I would really love them.

When some contributors wrote about delayed/irgnored payment requests (around two years ago) I rembember a technical issue. In the EU there was a change of the format of banking account (one large number instead of a combination of account number and bank ID).
On the one hand side a lot of contributors did not change the banking account number. On the other hand side - yes - there IT systems was not too smart. Instead of alarming/adressing this issue it seemed to be ignored.

Nevertheless: after changing my number and having a short telephone call with them I got my money.

At the moment it looks that the internal messaging doesn't work. My files wait since 8 months for release. Maybe my small number contributions have no priority or whatever. Of course I don't like this. But they exist, they can be reached via telephone and they told me about the new features they implement. I cannot say bad things about there reputation - only some troubles because of being a smaller organisations, yes.

Never submitted contents: I assume they have cooperations with other agencies. Like Eyeem w. Getty or Zoonar w. Getty, Age, Alamy or DepositPhotos w. ShotShop etc. Some of the agencies you work with will have subcontracts. DepositPhotos is known for giving you 0.30 cent while ShotShot licensed it and (sub)sold it for 22� or 24$. You have to disagree if you don't want it but submit to them with Deposits standard conditions (so far I remember, I don't deliver to them since that affair).

In my opinion it is improbable that ClipDealer took files without proper license. But if you have e.g. this DepositPhoto constellation legally/formally everything is right. Then it would be a Deposit/ClipDealer deal. To prevent this you should find the source and remove your stuff there or set a forbidden clause to the source of you can.