Well what I mean is not what RL or nGCD could do, but maybe. I've used Combat Archery with nGCD for a while and no issues, but have had issues with realism mods (hunger, thirst, sleep) those kinds that adjust stats.
Read this bit from the RL readme:
Recalculation will be delayed when the player is in combat. This is to avoid annoying levelups mid combat, and is explained rationaly as the need for some time to reflect before you can benefit from your experiences. However, recalculation is forced when a savegame is loaded to adjust for any changed config settings. This means savegames taken mid combat can suddenly trigger levelups when they are reloaded. It is also possible for levelups after long sustained combat to advance several levels at once. Recalculation can be forced at any time by setting aaRealisticLeveling.sumStats to 0 at the console.
Any mod that attempts to modify base attributes or health using "player.setAV" will have its effects removed at the next skill advance or message box. Only a small number of existing quests and mods do this, as the vast majority use "player.modAV" or fortify abilities which work fine with this mod and is the recommended way to do it.
Any mod that modifies base skills using "player.setAV" will affect attributes and level at the next skill advance or message box. If base skills are decreased this way, then attributes and level can go backwards. No mods should do this for temporary skill changes, instead they should be using "player.modAV", "player.modAV2", or fortify/drain abilities.
Most of those mods I've used - except AFC and only DR to a very limited extent.
So if there is anything using the methods above then it could be RL that is conflicting.
Thisiswar - have you confirmed the problem goes away when not using combat archery?