Well, the title says it all. When doing my testing on this issue, which can be found in the forum at this link: https://bygfoot.sourceforge.io/forum/viewtopic.php?f=1&t=945&sid=2ea8a0e76067f68d30f955c6262ac872, if you wanted to implement promotion and relegation within your country definitions, it would only work if your first instance of either was a relegation based upon league standings. Anything else and it would crash the game. A quote from my post in the forum is as follows:
"The results confused me as to have promotion and relegation work, the first code for promotion and relegation HAD TO BE within the <prom_rel_element> tag and have the value of "relegation" for the <prom_rel_type> tag. After that, you could use anything."</prom_rel_type></prom_rel_element>
So as some countries now may have promotion and relegation based upon a competition and not completely based on league standings, this error would not allow us to accurately depict that. Although why it was required was still confusing to me.