Using qsys2.ifs_read table function in RPG pgm and getting SQL0332 Character conversion message.

I'm trying to make use of the table function qsys2.ifs_read to read an IFS text file.
I have a test rpg pgm, with procedure, and when I used this syntax -
select LINE_NUMBER,LINE from table(qsys2.ifs_read('/myFolder/IB_Log_2021_Nov23Tue_10.09.43_AM.txt',256))
with hard coded path & filename and it works from 5250 session! Thanks IBM & rpgpgm.com!

I'm trying to switch the procedure to accept a path/filename and embed that in
the pertinent sql and it's stopped working.
This is the error message i get on the prepare -
SQL0332: Character conversion between CCSID 65535 and CCSID 1200 not valid.

I changed the job ccsid in my session thus - CHGJOB CCSID(37) and it works.

fyi We are at V7R3M0 TR7, DSPSYSVAL SYSVAL(QCCSID) reveals 65535.

Any thoughts, suggestions or explanations on why this is happening are most welcome!

tia
John

Here is the pertinent code...
dcl-proc #doIt_ThatWay ;
dcl-pi *n ;
pPathfile varchar(256) value options(*trim) ;
end-pi ;
dcl-s sqlstmt varchar( 512) ;
dcl-c apos x'7D' ;
sqlstmt = 'select LINE_NUMBER,LINE from table(qsys2.ifs_read(' +apos+ pPathfile +apos+ ',256))' ;
exec sql prepare stmt from :sqlstmt ;
exec sql declare mycsr cursor for stmt ;
exec sql open mycsr ;
...loop...
end-proc ;