No, it's definitely not the APN settings or internal settings (checked 100 times). This is the second time this year that the speed has suddenly dropped to almost 0 in the morning, 10-100 kbps (tested on several devices with their own SIM cards). Now, after 4 PM, it's also suddenly returned to normal. There's no information anywhere about any problems or scheduled maintenance. Very strange...and seems unreliable if you work from home.
