I recently purchased a new SC20H. The production sticker date is 2019-34. When depressing the On/Off button for the loop there is a substantial  drop in volume. Also, there is a hum present when the loop is in use. Additionally, when engaging pedals in the loop a popping sound is present. This is not something I have experienced  with other amps and I did not expect in what is marketed as a high end Made in England Marshall. This amplifier was produced  some time ago as evidenced by the date sticker. Have these issues since been addressed? I do not want to submit a brand new amplifier for repair. I am still under the retailers return/exchange period. Would exchanging for a more recent  production SC20H resolve this issue?