Unable to save resume file: Too many open files

[Faerch]

I have been using Transmission on my WD MyCloud PR4100 for about a year and a half with no issues.
But lately i have been getting the error "Unable to save resume file: Too many open files" and can't reach the Web UI.
Every time I have to restart Transmission, to continue the torrents.
Sometimes i can complete a torrent with no errors, but most times I get an error and have to restart Transmission.

When searching for the error, people usually mention too many peers or a corrupt hdd.

I have tried:

* To reinstall Transmission
* Setting max peers to 1
* Scanning the hdd for errors
* Removing all torrents and only adding one torrent
* Setting the resume file permissions to 0777 (but Transmission keeps resetting it to 0600)
* Closing down all other apps on the nas

But nothing helps and I have no more ideas.
I have several other apps running with no issues.

I'm running Transmission 1.07, installed from the nas app store.
In the Transmission Web UI, it says "Transmission 2.94 (d8e60ee44f)".

Can anybody help?

[Faerch]

Is there no one who can help?