Moonlighting at the bar is quit so often

Jeansoo

I searched on web but didn't find my case. My sim has completed his all mixology skill journal. He visited prosperous room for moonlighting. He moonlighted only for 30 mins in sim time, then I get the alert,"sweet. J earned 75 simoleons from moonlighting". And NPC mixologist is waiting her turn. So my sim got out of there, and visited Walyon's bar..(can't remember full name), and he just worked only for 30 mins there and get this alert,"sweet, J earned 15 simoleons from moonlighting". He was able to moonlight until 4 am for a few days at the beginning but as the story goes on, it happens like glitch. Is there anyone experience my case? I'm not using any mods related with mixology stuff.