How to connect from two PCs from a local network to a remote MySQL database?

Question

MySQL

Good afternoon! There is a MySQL server located on the hosting. A connection is created to it from a program written in Java + Hibernate. While one program is running, everything works fine, but if you run the program on another computer located on the same local network, after a while the connection is lost, after that it is impossible to establish a connection through other programs (Excel, MySQL Workbench), nmap shows that the port filtered. If I reboot the router, everything works fine. There is a suspicion that the problem is in the routers, the main router is located in another room, although all the locks have been disabled on all routers. Please tell me what can block the connection in this case?