I do get the sign "O" by KSC assembler if SJMP (and others +-127 b), as well as AJMP and ACALL cannot reach the related label.

OK the assembler can catch if an "A" is more that 2k from its target, but it can not catch if it does not end up on the same page. There is an obvious exception to this : The "linkerless" assemblers. However, if you are (much) beyond 2k program size, working with a "linkerless" assembler which, by definition, require all but includes to be in the same file, can become quite a hassle. In the pre-C days, I worked with the free metalink assembler, but as the project sizes grew, I gave up (after trying code in .inc files and who knows what else) and purchased an assembler with a linker.

Erik