Analyze Network Problem in small Network

Situation: Cable Modem - Synology Router (with WiFi) - TP-Link Switch Ubiquity UniFi AP AC PRO Access Point connected to the switch. Most Wireless devices connected to the UniFi. Printer, Diskstation, AppleTVs, Homeserver connected via cable to the switch. We have daily drop outs in which the UniFi gets disconnected from the network. In these drop outs the devices on the switch can still talk to each other and devices connected to the wifi of the synology router can still talk to the devices on the switch. However Internet is down. I have observed that Internet connection is lost first. Then after a short while the UniFi goes down and after 5-8 Minutes the internet connection as well as the unifi is back. I have a wireshark protocol taken from a laptop who was connected to the WiFi of the synology router. Additionally I have a log which logged internet connection from the same laptop. Furthermore I have the log of the Ubiquity UniFi controller, which shows the disconnections of the UniFi AP.