Why does the mouse begin to lag in the late afternoon?

Question

Mouse

Given: MacBook Pro Mid-2012 (Non-retina, upgraded to 16GB RAM and 500GB SSD), macOS Sierra 10.12.3, Magic Mouse (1st generation). I have been using the mouse for almost two years now and have not had any problems during this time. The problems started after I bought a Dell U2515H 2k monitor and a Magic Keyboard 2 to use the laptop with the lid closed.
After the purchase, about a week later, I began to notice that after some time using the computer (usually late in the evening or at night), the cursor starts to slow down periodically: it moves slowly or does not react at all to mouse movements for 1-5 seconds, after which it "releases" for 10-30 seconds, and then in a new way (and sometimes the connection is lost altogether). Also, at these moments, does not respond well to gestures.
The battery charge is quite high (> 70%), charged less than a week ago. I tried to reconnect the mouse, reconnect the bluetooth, re-pair - it did not help. Chopped off the keyboard, wi-fi - did not help. I connected a mouse with a radio module - there are no lags, but instead of them - sharp "jumps" of the cursor from one place to another at the same intervals. No devices other than a monitor and speakers (via a jack) are connected to the computer, to the monitor too. There are no lags on the trackpad.
The lag appears regardless of the level of workload of the computer. When a lag occurs, the performance of the system does not change. Rebooting helps to get rid of jamming, or sending it to sleep at night.
What do you think could be the problem? Thank you.

Answer 1

In general, as comrade 123459 suggested , it looks like there is noise from devices connected to usb3 ports on the monitor. Moreover, simply turning them off for some reason does not give a special result; in addition, you need to recreate the pairs. More details are described here: www.bluetoothandusb3.com/the-explanation
UPD: I solved the problem by moving the laptop to the right side of the table, closer to the mouse. Actually, this method is offered by the link above.
PS: Alternatively, instead of rearranging, you can shield devices (and ports), but somehow you don’t really want to wrap your phone and tablet in foil.

Answer 2

Gets tired during the day)))
I, for example, also start to lag in the evening) In the morning I’m fine, and in the evening I slow down :)))
That’s the same with the mouse)))