Uninstall the new java, install java 8 and run jarfix iafter that to fix your java settings.
https://johann.loefflmann.net/en/software/jarfix/index.html
Mirror can be very heavy for older systems, so it could be the case your cpu just can't deal with it. (Check taskmanager) OR maybe the script is designed in the wrong way
Use new mouse, it's great
Near which steps, the agility shortcut? I would recommend to NOT chisel while walking to prevent this
Missclicks can always happen, not much you can do about it, it might even be better for banns to throw in a random action in there ^^
Very weird, try to zoom in a little and see if that makes a difference, grab a printscreen of it aswell next time so I can take a look how it looks at your point of view
It's a mirror mode cliebt issue that can happen randomly for some reason, restart mirror client and it should be fine again
Let me know if you still encounter this