Unable to use firmware above 1v95 on Espruino Wifi

I just received my first Espruino Wifi which originally had 1v88 firmware. The device worked fine, I was able to connect to it and upload commands using the Espruino IDE on my Macbook pro without issue.

I tried updating to the latest (as of this post 1v99) and noticed extremely odd behaviour. My system would freeze up every five seconds for a period of 1-2 seconds, repeatedly unless the device was disconnected from USB. Additionally the Espruino IDE could no longer see the device on the connect screen.

I then tried downgrading the firmware to 1v98. I successfully downgraded, and no longer had the freezing issue. I was able to connect to the device in the IDE, but then when connected the terminal was flooded with the repeating messages over and over making it unusable.

Uncaught undefined
Execution Interrupted
Uncaught undefined
Execution Interrupted
Uncaught undefined
Execution Interrupted
...

I tried clearing the device to ensure no programs were running on it using the steps outlined in the troubleshooting docs in the section Espruino stopped working after I typed save() which unfortunately didn't help. I then tried downgrading firmware to 1v97, and 1v96 each of which did what 1v99 and 1v98 did respectively. I finally tried 1v95 and that worked as expected without issue.

Does anyone have any insight into what's happening here? I couldn't find anything any forum post with a similar issue.