Bulging 110mm flexi coupling - replace?

[KMD42]

I have a rear extension on my house where the previous owner boxed in the soil pipe with plasterboard. I recently started getting patches of damp coming through the plaster at the bottom of wall and ended pulling the board down. The concrete floor was soaked and the surrounding skirting damp. Running the taps produced a small leak on the bottom of the flexi coupling between the plastic downpipe and the old metal pipe from the floor. This may have been happening for at least a couple of years. I tightened the clamp and the drip seems to have stopped but the coupling has a slight bulge on one side (see picture), under which the leak was coming out. Not sure of the cause. The drain doesn't appear to be blocked but has been in the past.

Question is, should I replace this coupling before boxing the pipe back up or let sleeping dogs lie?

The plastic pipe is fixed into the ceiling I fear that replacement may involve cutting the plastic pipe and using 2 couplings? To add some jeopardy to the situation, I'm selling my house and have viewings in 2 weeks. I don't want to leave a problem for the new owners. Welcome thoughts please.

Thanks in advance

 

[denso13]

It should be ok if not leaking now. Probably not tight enough to begin with.

 

[KMD42]

Another picture to highlight the possible flex in the plastic downpipe. Although the last thing is want is to damage the seal in the roof.

 

[KMD42]

Thanks. That's the advice I was hoping for!