I have a bath with handheld shower attachment which was installed about 2 months ago. A few weeks ago the manual mixer valve tap stopped working - both the tap and the overhead shower spew water at the same time when the taps are turned on - it's not possible to only have one or the other any more. The pull/push knob still moves fully (i.e. it's not jammed halfway), it's just not doing anything.
The taps I have are these ones:
https://www.bathempire.com/ivela-bath-m ... TOHaSFViko
Is there something obvious I should check i.e. does the knob have a tendency to lose contact with the valve and something needs tightening, or is this clearly a faulty valve? If so, is there an easy way to swap the valve or is the only option a (rather difficult to access) tap change? The taps look like a closed unit to me - I can't see how you could swap out just the valve (but hopefully someone here does!)