Appreciate your dilemma. It surely has to be the PSU.
I would not ignore the problem which if it is the PSU, could pop other things if or when it dies.
In view of the distance snag, can you email the firm for advice?
In my opinion you could use virtually the same words that you used when starting this thread.
Of course it may be something else, but the ticking noise is probably something cooling, and the flickering lights go on for much too long if you really have isolated the set from the mains supply.