I try if I can save it to thumbdrive or other external storage. I am using development version so should be ok to locally access.
@Shuuri, in case you find it easier, as you are using a development image, if you have a Windows or Mac laptop, you could enable internet connection sharing on the laptop (docs for Windows, docs for Mac) and connect the RPi to the laptop with an Ethernet cable (in addition to the WiFi configuration). The device will then probably show up on balena’s web dashboard, accessing the internet via the laptop. Then you can ssh to the RPi with a command like:
$ ssh -p 22222 root@X.X.X.X
… replacing X.X.X.X with the device’s IP address, shown on the web dashboard.
Then you can run the journalctl command mentioned by Shaun, in the ssh session, and copy-and-paste it. Even though the device will be connected to the internet via Ethernet, the logs should still include WiFi errors.