Hello tuk66, and thank you for your reply.
It is quite a strange problem that also happened during our migration to the 1.7.6.1 staging environment, so we had to change the order friendly URL to fix it, the same applies to our recent migration to 1.6.1.24, but it seems that some, but not all of our customers still see a 404 page in some cases.
There are also no server errors in the log.
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