Blynk is constantly communicating across the device, unlike some other apps or programs. This will make hardware instabilities stand out quicker.
I ditched mine years ago as even USB link was super stable compared to my Chinese Ethernet adapter… which did work with basic Arduino examples, just not with Blynk’s constantly-in-use link.
The adapters are generally the issue, particularly the Chinese clones. Many using the Arduino original ethernet shields, and even some lucky clones, can run with that library and no issue… others find them unstable if you look at it sideways.
All this means is that you just rebooted the Arduino… that is a normal result when opening the Serial Monitor with an Arduino.
You can search this forum for some possible “After Blynk disconnection, keep code running and attempt reconnection” options that will even work with Arduino with shield (although generally meant for ESP and WiFi)