yes the handle has come loose and have been told has got tight so may need a service kit and maybe a new thermostatic cartridge , am a plumber and heating engineer fo 42 years but havent come across this mixer before , i think it is approx 3 - 4 yrs old
Swirl is screw fixes own brand - might be worth giving them a call, although a few months ago they told me they dont supply spares for their swirl bar mixer shower & I should just buy a new one - I did but not from them!