Thanks for your quick response Ananda. I'm playing the game since 1.5.7 stable version, if i recall. Everything was normal
with or without mods, until 1.5.9. Since 1.6.0 was released, everything messed up. Since then i've started new campaigns everytime TaleWorlds realeased a new version (due to the incompatibility of mods with each new version - Yes, playing with mods like Freelancer, RBM, Diplomacy, Calradia Expanded, Improved Garrisons, AttributePointPerLevel and some other mods, which should be included on the standard game core, improving the game way better) just to see if my issues was resolved but no, there was still there, even if i played a considerable amount of game time. I've contacted with every modder, but all of them was saying that their mod had nothing to do with the spawning time of items, nor with which city sells what.
Anyway, i'll wait some more ingame time to see if anything changes. If not, i will follow your suggestion. Thanks again for your reply