How to reproduce the bug:
Put an item with a long name, in the screenshot: "Arrow of fire resistance"
In the GUI, it's displayed "w of fire resistance" as explain is MC-1237
If I switch the Arrow of fire resistance with an anvil without taking the Arrow of fire resistance before, it will be written "l" with characters missing as with the Arrow of fire resistance.

Only happens if the new name doesn't become fully cut off.