This does sound like a network problem. More details are needed to help there.
You may also find some helpful ideas here in the KnowledgeBase.
For the Dell Inspiron you are using as an endpoint, what Roon program are you running? A full version of Roon or RoonBridge? If it’s used as an endpoint only, you only need to run RoonBridge. There is a lot less going on in RoonBridge than Roon, so there is less to go wrong.
To answer your second question, there are a ton of endpoint solutions out there, across a wide range of prices. I built an endpoint this weekend that was a Raspberry Pi 3B+ board, HifiBerry Digi+Pro and a metal case. Output is SPDIF (Optical) and its running Ropieee RoonBridge. Works great. ~$130