There seems to be a few issues, which might be related, not sure.
First issue is the "overload-protect triggerred" error that started a couple of weeks back. Affects posts with embedded media. Seems like a server end i/o resource/bandwidth issue. I suspect some new scripts were introduced in the background about 1 to 2 weeks back.
The overload-protect error has largely been fixed, which reveals a second issue. After playing embedded media in threads, some script is run on the users' browsers. This causes the browser to visibly lag. Scrolling lags and is no longer smooth, when typing replies, every character typed appears only after a delay, even liking or other reactions to a post lags.
This sometimes results in a 3rd issue - the reaction/reply doesn't get commited on the server end, and the server throws out an error to inform users. Error message is similar to what happens when posts become locked, even though they are not.
Finally, the site loads halfway as if there are loss packets, loads slowly or perhaps the entire site will even stop responding intermittently. This last one could be due to server being overloaded or could be due to DDOS attacks.
Not sure if all the above are linked to the same root cause. Though they did seem to have started a couple of weeks back in sequential order.
Maybe someone can have the admins take a look at what changes were implemented the last 2 weeks.
Edit: Just got hit with the error when submitting this reply. It's the "Opps! We ran into some problems. Please try again later" popup message from the forum engine.