[Update for future generation]
I think I found my issue. It was the large transceiver see image below, with power amplifier and external antenna.
Once I replaced both receiver and transmitter with identical units, range got significantly better.
60m clear sight and almost whole house through multiple walls.
For whatever reason small unit can't hear ACK from the PA unit. I tried to reduce power on the PA end to
but it did not seem to have any effect. My best guess now is that oscillator on the PA unit is slightly off. PCB antenna unit is battery powered.
Power source to arduino UNO that drives PA unit is good, 5V less that 2mV ripple. The transceiver is powered via 3V3 output (onboard regulator) of UNO though, could it be the problem?