Showing A Post Has Been "Read" Is Inconsistent

[Gary Lewis]

We have a strange problem where Nabble is showing that threads have been read when using one machine/browser combo and not read when using another combo.  And some combos don't even show the whole page.

Safari on my iPhone X is the only one that appears to work correctly.  On my Windows 10 device Chrome gives what is shown on the left below, which is obviously not correct as it shows that I've not read my own post at 5:43 PM.  And Firefox gives what is shown on the right - which is only the first 3 items of the page in Topics View.  On the other hand, on my iPhone X Chrome gives the same thing as Firefox on the Windows machine - only the top three things.

My members are telling me that this has been going on for maybe a month, but have only just alerted me.  Can you help, please?