no. there are diffrent models with the same issue.
I'm now pretty sure it has something to do with the network configuration. pxe server is in another subnet/vlan than clients. I did a test with a client in the same server vlan and it worked all the time.
I tried setting an ip-helper but that didn't solve it. I'm digging deeper since the issue has to be in the network imo.
if you have any experience or tips that would be much appreciated.