Epson LQ-860 User Manual page 137

If you define characters in one mode, then switch to another mode
and select the user-defined character set, the command is ignored
and nothing is printed. The user-defined character definitions,
however, remain unaffected. If you switch back to the mode in
which they were defined, you can then select and print them.
Keep in mind that user-defined characters are stored in RAM, which
is not permanent memory. When the printer power is turned off or
the printer is initialized with the INIT signal, the user-defined
characters are lost. (Some computers do this each time BASIC is
loaded.)
4-30 Software and Graphics