I have a problem with added servers disappearing. I add the local LAN server to the tablet and click save my children then play on the local server. The problem is when they try to connect to the server again the servers details have been removed from the server list. 

The commercial servers are all listed (Cubecraft, Galaxite etc.....).

The issue is on an Amazon Fire HD 8 (7th Generation) tablet (Kids Edition). 

OS Versions tested: Fire OS 5.6.7.0

Minecraft Version: Bedrock Edition for Mobile v1.16.100 (Also happened on previous version) and the latest 1.16.200 update

Steps to reproduce: 

Open Minecraft

Select Play

Click the Servers tab

Scroll past the "Featured Servers"

Click Add Server

Enter the Server details. 

The entry is added the the Additional Servers Section

Click on the Server Name

Click Join Server

Play the game

Press back

Save and quit to disconnect from the server

Press back until you get the confirm you want to exit Minecraft screen

Save and quit

Choose OK to Exit Minecraft

From the main screen click on the Minecraft icon to re-open the game. 

Once loaded select Play 

Choose the Servers Tab

Scroll down to where the additional servers saved earlier should be and the entry has vanished requiring all the details to be re-entered.