Cursor's position lags out and resets

Playing normally on both Windows and a Distro of Linux called Solus (great guys, absolutely love them), the same issue persists, although on Solus more severely than on Windows and considerably more often.

The issue itself is that whilst destroying blocks successively (as in one after the other in rapid succession), such as when mining a tunnel, no matter the worlds I'm in (nether or Overworld), sometimes the cursor just resets to a previous position, sometimes deleting some of the progress I made (a little bit, in Windows' case).

On Linux, however, this issue is more severe: I noticed it happens more in my Overworld, possibly due to the number of mobs present around me?
The cursor does not just move back to a previous position, it instead looks down below the player. I not once dug/mined below me by mistake, which when making a bridge in the Nether of a lake of lava would be particularly dangerous.

In the game it does not show, however, that the RAM is fully occupied, although I think it might happen because I use Linux on a pretty old setup, with only 4Gb of RAM, of which Minecraft alone reserves 2.4 Gb

On my Windows setup, an HP Laptop, I have 8Gb of RAM, and about 3 if not nearly 4 (I have seen the graph but did not check the numbers) are reserved by Minecraft.