The reason you are getting kicked / losing connection is because you are using a client version which is not yet compatible with Jartex i.e. 1.19.3
JartexNetwork is not yet entirely compatibly with 1.19.1+ java versions (1.19.1 is compatible)
Only bedrock players can join using 1.19.3 as of now, so it is recommended not to use 1.19.3 java in first place
And even in 1.19.1 annoucement there were warnings about possible chat issues
So for now please try to stick with 1.18 or atmost 1.19.1 as it gives you the same access to Jartex as any of the higher ones will
Its not a problem just from your side as it happened to me too when using 1.19.3
Funny thing is it doesnt happen with 1.19.2 users, so its a 1.19.3 specific bug
You may make a bug report with proper evidence (full screenshots and recordings) over at
jartexnetwork.com
so that developers will be able to create a better support for 1.19.3 in future
Few
others have also faced this issue so there might already be some bug reports made