little off topic but looking for help with digital clock

I hope an electronic wizard here can help! I purchased two large number digital clocks, they worked fine. One is in my shop the other at my home. Clock at my shop is still working great. The one at my home is on second floor about 6' above the floor. Power from outlet via transformer is directly below. My numbers started blinking, at first I thought clock was going bad, possibly when time above 9:55 more power was required. I tried disconnecting all power connections a few times in an attempt to make better connection. Then I noticed at night no matter what time the clock is fine. Soon I noticed it will run OK until 10AM, blinking starts and continues to about 9PM then All works fine again! Other devices plugged into the line work OK including a large number digital alarm clock though the digits are not as large.
Anyone have a guess as to why?Nothing in my home turns on or off at that time nor do I have any problems with anything else including my computer!

You get a pass this time........

Any chance there is a photo eye to sense light conditions? If so, in daylight the LEDs would be brighter, and at night dimmer, that does seem to coincide with what you are seeing.

No photo eye. Light level has 2 setting I have in on low. Light level in the room at night with lights on is about the same as day with lights off. I get no flicker in the clock at the shop, light level about the same maybe brighter with all lights on as usual. Morning sun shines in the window so early morning light is greater than afternoon. Cloudy day darkens unlit room but has no effect, problem seems to be time related, only started doing is about a week ago, has been working great for about a year. I'll bring home a volt meter, maybe the voltage drops during the day due to some business. Transformer power supply is 5VDC I think, didn't look but the cord has USB-C plugged into power supply. Might be that line drops 10% maybe little more but computer no effected but if power supply is unregulated (not very big 1" X 1" X 2") could lower supply voltage enough.

Swap the clocks

See what happens

Or swap power supplies if they are plug-in type.

Swapping clocks is easier said than done! Shop clock is up 13' above a wall mounter work bench. Not easy to get too! Shop is all Metal building would be easy to just take the clock to the shop and see how it works inside metal building. I'll do that tomorrow! Forgot to bring my volt meter home will do that tomorrow too. Not sure I'll have to check, I have a wireless mouse for my computer, I have noticed it wants to double or triple a number entry in the computer calculator I use mostly in the day, check it now while the clock is working normal, no double or triple entry! I'll try it when clock is flickering tomorrow at 10AM.
Up-Date; Watched the clock today, flickering started at 10:00:00 AM, 9:59:00 it was OK! Checked the calculator on the computer at 10:04, number input is not doubling or trippling.

Does your power company inject any timing signals in mains power?