Tvheadend

I might have had this problem for a while as I don't tend to watch these channels via Kodi, but when i try to change to channels on Muxes one of 4 my four tuners isn't already tuned to I get the error

Error: TVheadend HTSP Client no free adapter available

https://pastebin.com/6PmKXEs4

I've checked in status/stream and I can only watch channels on a stream a tuner is already connected to. Any idea what's wrong? Luckily the channels my wife watches are tuned, so she isn't aware yet I think.

I'm running the linuxserver default docker and a TBS6205 watching Freeview in the UK.

System spec:

Xeon E5-2683 V3, ASUS X99-A II, TBS 6205 DVB-T2 Quad Tuner, latest linuxserver docker 4.2.6-34~g81717d98d