The issue that this customer was having was most definitely related to SH404SEf. We explained to him that our extension was compatible with all popular SEF extensions however SH404SEF was very common to producing issues with a lot of 3rd party extensions, not just ours when it can wrongly cache a URL. The issue this customer was having was not produced or caused by our extension and he was not using the latest version of SH404SEF. We told him to switch to the core SEF setting to prove to him that this was in fact an issue with SH404SEF and that our extension does in fact work fine with SEF settings enabled. We explained that we could not be responsible for a 3rd party SEF extension that was overriding our extension. This customer was very rude and condescending to our support staff right from the beginning and had no just cause to act this way as we were very professional and courteous in our support.