Subscribed Topic stops

Hi,
I am running Hass since years. I have a weather station (ESP8266 based) too since years
Working fine.

Now I programmed (ESP8266 based too) getting the local (room) temperature and humidity from a DHT22 Sensor and publish this to Hass. Works fine since months.
I extend this to show these values on a local TFT Display, so far OK, I extended this by subcribeing the weatherstations temperatutre, humidity, pressure and sun.sun. and display this information on the TFT. Works too, but after some hours, at least more than 6, I still get local valus on the display and published to the HASS MQTT Broker. but receiving subscribed topic stops.
I use the bblanchon/ArduinoJson@^6.21.4 and knolleary/PubSubClient@^2.8 libraries and my IDE is PlatformIO

Does anyone have an Idea, why syscribtion stops.

Thanks
Rainer