Solved Question

@est12 , you probably have some connection issues as the server is just fine. Most likely your internet connectivity is spiking so be patient and your ISP should deal with this.
When it comes to hosted services on professional dedicated servers please keep in mind that there are more chances for the issue to be on your side rather than the server side. Our dedicated server has a 1Gbps connection.

 

Sometime your MU window might deactivate so just click it twice in taskbar, it rarely happens when I do alt tabs frequently but not sure you had this.

There is also a serverside anticheat prevention when moving items too fast or when the server feels like you are trying to do some illegal action and your inventory might get locked temporarily and this is what probably happend. If you can type and send messages in chat without a delay then it's not a lag issue.

Example: 12:25:59 [CMD ANTIHACK][xxxxx][xxxx][Map:2] Inventory is locked!

This is a prevention system that just blocks a possible action, it doesn't mean that the user has actually broken any rules.

Also a small delay of 500ms is added when transfering from vault to inventory and viceversa in order to prevent cheating attempt. I've noticed others use a whole 1 second (1000ms) but thats not needed and 500ms would suffice.