Best method to check your clutch cable tube, should it move @ all with pedal depressed? Options

[porschetub]

As I have my g/box popping out of 4th gear I'am lost for a reason as everything has been done externally,Tangerine bulkhead bush, x 2 shift rod uni-joints and double oilite console bushes.
Shifts all other gears fine and down changes fine however have issues with a new cable that has needed constant adjustment since fitted it after a short time so thinking now the tube is moving in the tunnel due to the mounts breaking further.
Thanks to a fellow NZ member on here I have got the contact for the leading guy in my country that works on these transmissions but TBO don't want to send it to him for assessment if its not an internal problem and can least afford to do that.
Will add that I have new clutch with clutch throw out arm rebushed and new mounts but when last checked I noticed the tube was moving a little with pedal depressed.
TIA.

[Superhawk996]

Tunnel internals.

This donor tunnel that I obtained had broken loose at the front (2 J hooks in place from what ever car this came from) and the stamped steel bracket that the tube mounts to behind the shifter is also torn and fatigued from the front having gone too long before being fixed.

Per Clay's comment, the tube needs to be rigid all the way, front to back and it will deflect from side loads. Without a rigid tube, you will have lost travel at the pressure plate and constant adjustment issues.