Patch Track Direct to Track Input Not Working

Any ideas where I'm going wrong? I've used this feature for years without any issue, now I just cannot get a single patch to be audible. Screen grab animation below shows the issue as simply as I can demonstrate. I have default monitoring set to Input, Path settings to Thru and Direct and track A is patched to track B and track B is outputting to default Bus1 which is audible when simply routing track A to Bus1. Can't make it any simpler, but the only success has been Track Reproduction rather than Track Output but that only allows one track to be patched then it falls over and mutes all audio and you get the odd glitch like static clicks.

I am struggling with a similar issue, just get it to work with Track Reproduction.

I think it must be a bug in the latest version. Track Reproduction only works for one Patch. Add a second patch and all audio is off even though the meters are all working.

I am still on 17.5 and never used this feature before. Tried a few weeks ago and had the same results...

I've no idea, it's getting me in a rage as I've been battling at this all morning to do some Fairlight work. Gonna give up and move on I think.

On macOS both Track Direct and Track Reproduction allow multiple patches and all destination Tracks successfully take an input from either source and that input may be monitored.

On Windows is this behaviour in 18.0.3 present with both ASIO and WDM?

I've tried both ASIO and WDM and neither work for Track Direct. Track Reproduction allows one track to be patched to another in ASIO, then nothing it wipes all audio out even though playing and on the meters of the source tracks. WDM appears to allow multiple patches, but only the first one is clean audio, the second just sounds like it's stuttering.
Does this feature require a Duplex ASIO device or is it routing internally? I did think the unusually high latency suggests this isn't internal routing, but going outside and back in again.

I've just tried with a 64 channel Duplex ASIO device. Track Direct still doesn't work, not even one track can be patched. Track Reproduction does allow one or more to be patched, but as with WDM & Non-Duplex ASIO device all audio is wiped out on the main output bus including that not patched, just a normal audio track outputting to it. As before you just get random glitches of static, all meters show as working,but nothing audible.

Identical behaviour in both Fixed and Flexi Bus Projects on Windows?

I haven't tried Fixed bus, but I've never used Fixed bus and Im sure this worked. I just tried patching 10 tracks to 10 other tracks, but no joy, it doesn't fall over, there's nothing in the logs, but patching wipes out the audio at the output. I'll try Fixed bus. Here the 10 tracks patching. All plays fine, just no audio gets patched and kills the audio that should be playing with it.

OK Fixed bus works for patching from Track Reproduction, but Track Direct is the same as Flexibus and not working.

Well Track Reproduction lasted about 10 mins until I added some more patches then it all fell over again. Playback fine, meters all showing what they should, Patch I/O all showing what it should, but just no audio getting to anywhere you've patched to. I give up, I'll have to do the audio in something else and then bring it all back in as stems. What a waste of a day! I spend more time with the audio than anything Video in Resolve, it's fine when it works, but Fairlight just feels so unstable when it comes to doing anything a little more than just dragging an audio track onto the timeline and hitting play, it's such a shame.

Rolled back to 18.0 same issue, everything looks like it's working, but no audio when using Track Direct. Track Reproduction also looks like it's working, you get a very occasional glitch of audio and one track will patch, more than one and the audio stops. I can run over 100 tracks of audio no problem directly to various busses, through VSTs etc, just can't get anything patched.

Logs, system info and video showing issue are attached at we transfer link below. I've tried a MOTU, Realtek & Apogee ASIO Interfaces, including WDM options where available, but same issues with all of them. I have no other audio issues on this system, regularly mixing 20-30 audio tracks in various DAWs, VST and audio over ethernet syncing quite happily with minimal latency.

https://we.tl/t-nNPJUNo6vj