System booted to the above startup screen. Cursor was blinking and the computer was operating, but character graphics were messed up. After a new U5 chip was swapped in, the fault was gone, however it did not reappear after re-inserting the supposedly faulty chip. It turned out the U5 had been poorly seated in its socket, and removing/re-inserting was what actually resolved the issue. NOTE: the same symptom can also be related to logic chip U26 as shown here
Bad socket contact on U5 (Character ROM)
