AdiIRC

I've been using AdiIRC for a few years (currently using version 3.6 Beta Build 2019/07/10 64 Bit), and only in the last five or six weeks I've had this issue (and solely with AdiIRC):
other users' messages arrive to me regularly, but when I'm the one sending a message, it runs after a variable time; in better moments, all messages lag just a few seconds; in worse moments, they can take literalli a dozen hours, perhaps more.
This gets significantly worse if I'm running some other program that is constantly connected to the web or open certain sites (this one with sites doesn't always happen, but usually does, while the other programs one is 100% sure to occur), like YouTube.

Why did I say "it runs" instead of "it arrives to others"? Because, as I've thoroughly tested, it's not that the messages are sent, remain in some web queue, and then arrive, but rather they remain on a sort of local queue; they're as if they were never inputted into AdiIrc. It lets me write them normally in the input area, but once I press Enter, they just disappear.
You know, normally when you send a message and then press the up arrow in the input area, that last message appears, and previous messages as well, if you keep pressing up; but when this thing happens, the messages can appear there only after they have finally arrived to the recipients; before that, it's as if I never even wrote them.

Also, when this happens, if I wrote multiple messages, when they finally arrive they're in mixed order (usually reversed), not the order in which I inputted them.

Any idea why this issue popped up and how to solve it to get a normal functioning AdiIRC like before?