SBC status change UP only message but no DOWN message comes , Why ?

[BABALUCHA]

Hello Everyone , First of all thanks for stopping by and checking this out.
Quick question , i have a customer who has a shitty internet connection and it is shared between about 6 computers , 3 printers and 1 AP, 1 SBC (raspberry pi4 with 4GB ram) , 5 Fanvil X4U Ip Sets , 1 Grandstream HT801 and about maybe lets 4 smartphones that connects daily during business hours. So it is a small business and the bandwidth is only about 2Mbps and about 800Kbps up ( not great internet , due to the area they are in and that is best they can have with wire PPPOE connection ) They are using Ubiquiti ER-Lite and HP Switch and one more D LINK 8 port switch in the network .i know i have mentioned every single device in this but i wanted to do it in case someone has a question about the load on this internet connection.
My question is that WHY I RECIEVE THE ATUMATED EMAIL NOTIFICATION FOR SBC TO GO UP ONLY AND WHY I DON'T GET THE EMAIL NOTIFICATION FOR IT BEING DOWN .So at this point you guys think if this Raspberry Pi 4 with 4GB power goes down or it is simply just constantly pinging to the 3cx PBX Hosted by 3cx and whenever it can't get through it logs it and when in ( lets say within a next second ) it is able to ping than it sends me a notification that the SBC has status changed to UP.
Again sorry i gave a lot of info in the description to help and determine what could be the cause . Again thanks for your input everyone

 

[SteveITS]

This comes up every so often here. The Up message triggers at every reconnect. The Down triggers every 5 minutes. So an Up is a very short drop.

 

[AWS2P]

isn't it possible to have a better connection with 4g router ?