The number of recruits is not a bug. If you are not satisfied with this, then you can change it.
To do this, go to the following path steam(steamlibary)/steamapps/workshop/content/236850/2227743919/common/defines
here, open NDefines.lua with notepad and find the line "MAX_MANPOWER = 20" and change the value to 10 (as in the standard game). this value is responsible for the amount of years to restore the entire manpower from 0.
You can also increase the total number of manpower by changing the parameter "BASE_MP_TO_MANPOWER" in the files Defines.lua and CUSiegeDefines.lua (this parameter is responsible for the number of recruits, which gives 1 unit of agriculture). In the standard version, this value is 0.25, but in the mod you also get recruits for commerce and production, so i advise you to put 0.125-0.15.
I also advise removing the manpower bonus for the ai, otherwise they will have an incredibly large number of manpower.
to do this, go to the common/static_modifiers folder and open the cu_static_modifiers file. Find "difficulty_normal_ai" there and remove "global_manpower_modifier = 1.0" there.