Shrinking guttering joints

[Corazones]

Hi everyone,
Maybe it's just the cold weather, but my half-round plastic guttering (professionally installed several years ago) has shrunk apart in the central joint of long runs - both at roof height and on a ground-floor extension. In the latter case which is easier for me to reach, I have tried everything to cure it - unclipping all the joints and closing them up, even though it left the gutter a fraction short at one end ... but still it opens up again. In desperation I drilled a short bolt through each end of the bracket and gutter, and sealed over these, but surely that shouldn't be necessary! What is the answer?

 

[Alastairreid]

They have been cut to short when they were installed.
The only remedy is to replace the affected lenghts.
Guessing they are black or brown.

 

[^woody^]

Fitting another joint means that the gutter does not need to be replaced, as the space taken by the aditional joint, cancels the shortness of the length of gutter.