need help with my CB360t charging system

bought a CB360t in good conditions, everything works just fine but the charging system was flawed. The battery I uses is a TTA 12v, but when charging there is only 7 volts charging. I replaced the rectifier and it functioned fully for a duration of time, but now the problem came back and I can hardly start the bike with kick start. The battery is brand new and the rectifier is brand new and everything worked for a good amount of time I just have zero idea what can cause this problem. Does anyone have experienced similar issues and how you guys fixed it?