Great question — answering as the UphillTech team:
After doing some research I found this which is a near identical situation: https://community.screwfix.com/threads/soil-stack-branch-replacement-help-please.239968/ TLDR; Attempt to rotate the branch, this maybe possible if it is pushfit. If it won't budge the branch needs to be cut out by making two cuts above and one below. Clips and straps are needed to secure the soil pipe while doing this. A slip socket, or a flexible 110mm connector (with jubilee clips) will be needed to fit the new branch in the new position.
Full answer by thodic: https://diy.stackexchange.com/a/305405 (CC BY-SA 4.0).
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