Does your on-screen keyboard automatically show up when you start editing the port number?

In the current version(5.2.0), when a window "resize" message is triggered while editing the value in property scroll, the editing box gets removed. And, on-screen keyboard triggers that "resize" message.

So, when you start editing, an editing box shows up, and then on-screen keyboard pops up, this on-screen keyboard triggers the resize message, and this forces the editing box to be removed before you have a chance to enter a new value.

In order to work around this problem, please try activating on-screen keyboard before editing the port number. (For your information, the upcoming version will address this problem and retain the editing state even if a resize message is received.)

Hope this helps.