Roon version 1.5 build 363, Mac version. Core is RoonQNAP, MacOS10.14 Mojave, iOS 12 on a new iPhone XR. Playing through Meridian 218s to Meridian DSP 5200 and DSP 3200. Can’t recall exactly when I noticed the problem, probably within the last month or so. (I haven’t had a lot of time to listen to anything other than Sonos or radio recently.). I tried Roon on my Mac instead of the iPhone and it did the same thing: First it says “This track is not available from Tidal” and then the second message, “Transport: Too many failures. Stopping playback.” I haven’t tried every album, but every one I tried gets the same message, whether it’s a rock or jazz standard or something off the beaten track like Gordon Bok or John Fahey. My own albums on the QNAP play perfectly well.
Hope that helps.