This eems to be similar problem to this post.. https://helpcenter.websitex5.com/en/post/256452
I have updated today to 2023.2.3 and as per the post above , I have done a full all files upload to server but problem is the same.
then redirecting you to previous page appears under that twice.. Then reverts back to contact form page.
My clients customers on 2 occasions a few weeks back, have completed the contact form but nothing was received back from the client. So that contact system has stopped working..