Getting strange character output in PuTTY on one Ubuntu machine

[Bo Berglund]

I am probably missing something simple but I don't know what...

I have multiple Linux machines (like 10+) including PC:s using Ubuntu 18 and 20
or Raspberry Pi:s using Pi-OS.
I access all of these using PuTTY from my Windows PC and all behave sensibly
except for one Ubuntu 20.04.2 LTS PC on which the PuTTY output always is using
strange characters instead of normal ones:
For example when using "sudo apt update" I should get this as the final result:

Fetched 3 675 kB in 1s (2 804 kB/s)

But instead the space in the two numbers 3 675 and 2 804 is replaced by a square
box!

It seems like everywhere Ubuntu displays a number it uses a thousands separator
shown as a square box.

If I type the Swedish special characters åäöÅÄÖ into PuTTY the response is
correct, so the locale must be set correctly, I guess...

What can have happened for this particular Ubuntu machine?
And what can I do to fix it?


-- 
Bo Berglund
Developer in Sweden