Tabby showing diamond with question mark... sometimes

[JapanIsShinto]

Version: 1.0.197
Platform: Windows x64 10.0.19045
Plugins: none
Frontend: xterm-webgl

I am seeing odd behavior with Tabby when rendering Unicode Braille characters. When it does this, it will often display a few of the characters with a diamond with a question mark on it. Importantly, this doesn't happen all the time, and when it does, it will be in different parts of the screen. So that tells me that it is correctly rendering Unicode Braille characters. So this isn't an issue of not having the right encoding or font.

This is what the output looks like when I'm in the console under Ubuntu. In this image, there are three histograms rendered using characters. The first is using Unicode Braille characters, the second is using Unicode Block characters, and the third is using plain ASCII text:

Now look at how Tabby rendered the first one:

Again, this isn't consistent. Here is the same data, but notice the Unicode errors are in different places:

What could be happening here? Note that Tabby is connecting to an embedded Linux system over the serial console port using a FTDI cable at 115200 baud.

[JapanIsShinto]

Incidentally, if it helps, here is the actual data I'm sending over the serial channel:

histogram.gz