Text changes size randomly

Here's an image I just created:

...from this:

+----+ +----+
+ 3.0| | GND+
+----+ +----+  

...using:

java -jar /tmp/ditaa-0.11.0-standalone.jar x -o out.png -s 0.75

The 3.0 text and the GND text are different sizes --- if I render as SVG, I can see that the 3.0 is 10 point and the GND is 7 point. In the full diagram (of which this is a snippet) it all looks really weird. The -s 0.75 isn't necessary, but makes things a bit more obvious as the small text is much less bold than the large text.

This is on Debian with openjdk 11.0.6-ea 2020-01-14.

Do you know what's going on (and more importantly, how to stop it)?

(edited post because I uploaded the wrong image...)