Hi @Judelow
I am NOT an expert on this, so please take the following as just an idea:
As far as i could find something about it, Read/Write speeds are quite slow
3.100 MB/s / 1.600 MB/s
For my i7 NUC I use a Samsung 970 EVO Plus 250GB M. 2 SSD
3.500 MB/s / 2.300 MB/s
The following thread might be interesting for you:
One more idea:
Could it be that this ISP router is a bit underpowered and overloaded? ISP routers are usually not the most suitable.
Furthermore, your NAS, does it have enough power? I don’t use a NAS myself, but a fast internal SSD in my NUC, which is probably faster.