MyCloudEX2Ultra won't stay connected for remote connection

hello all,
i have an Asus Rt-AC3100 Router, MycloudEX2Ultra and a WDMyCloud.

the problem i am having is the following, the remote connection to my EX2Ultra keeps loosing the connection after about 15-30 minutes. My WDMyCloud has no problem, I can always gain access to it remotely.

the only way i can regain access to my ex2ultra, it is to turn off the " Cloud Access" from the settings, then enable it again. then its ok for about 15 to 30 mins then it kicks the error (connection failed 900).

the only thing i can see that may be a problem is:

when looking at the settings for both of the drives, the default ports are both set at 80 and 433.

other then that, the settings on both are the same.

thanks in advance for any suggestions.

You could refer to the following link: Error