[kallikles]

I had to reinstall LIbreElec/Kodi (v18) on my Raspberry Pi 3 due to corruption of the media card.

Unfortunately I now have a problem that did not exist before: The video image  goes blank for a second or so with no discernible pattern before returning. It happens about once every 15 minutes, but sometimes more frequently (every couple of minutes). It *always*  happens, no matter what Kodi is showing---when playing videos, when just navigating the interface, etc. Any ideas on how I can troubleshoot the issue?
Where should I look?

[Klojum]

To receive meaningful assistance you will need to provide a full debug log.

The instructions are here... debug log (wiki)

If you are using the Basic Method, then ensure the following is applied...
1.Enable debugging in Settings>System Settings>Logging,
2.Restart Kodi
3.Replicate the problem.
4.Upload the log to Kodi Paste Site manually or use the Kodi Logfile Uploader. (wiki) With either method post the link to the log back here.

If you are using the Advanced Method ensure you have correctly created and applied the advancedsettings.xml file (wiki)

In both instances, you should see the word DEBUG throughout the log.

Note: Full logs only. No partial or redacted logs
Do NOT post your logs directly into the forum. Use the Kodi Paste Site. Post the link to your pasted log in the forum

[popcornmix]

Hdmi cable sounds most likely. Try swapping it. Using another port on TV or connecting to another TV and see if it still happens.
Could be power supply (any lightning warning symbol popping up in top right corner)?

[kallikles]

Hdmi cable sounds most likely. Try swapping it. Using another port on TV or connecting to another TV and see if it still happens.
Could be power supply (any lightning warning symbol popping up in top right corner)?

I had checked the cables already and they are not the culprits. It could be the power supply---I do indeed have a lightning bolt symbol in the upper right corner. The power supply I'm using is rated at 2.1A, though, and in fact it is the same one I was using for the previous incarnation. Perhaps there is something wrong with it. Is there any way to check its max load? I do have a standard multimeter, but nothiing fancier.

[ActionA]

https://www.raspberrypi.org/documentation/faqs/

Pi 3 requires 2.5A.

[popcornmix]

I had checked the cables already and they are not the culprits. It could be the power supply---I do indeed have a lightning bolt symbol in the upper right corner. The power supply I'm using is rated at 2.1A, though, and in fact it is the same one I was using for the previous incarnation. Perhaps there is something wrong with it. Is there any way to check its max load? I do have a standard multimeter, but nothiing fancier. 

Multimeter can measure the 5V voltage on gpio header (https://www.raspberrypi.org/documentation/usage/gpio/)
but it will be below 5V when kodi is busy (technically it is instantaneously below 4.6V for the warning symbol to appear, but you may not see that on a multimeter).

This is a known good supply: https://www.raspberrypi.org/products/ras...er-supply/

Unfortunately a lot of power supplies (especially cheap chargers) don't deliver the volts they claim under load.

[kallikles]

I had checked the cables already and they are not the culprits. It could be the power supply---I do indeed have a lightning bolt symbol in the upper right corner. The power supply I'm using is rated at 2.1A, though, and in fact it is the same one I was using for the previous incarnation. Perhaps there is something wrong with it. Is there any way to check its max load? I do have a standard multimeter, but nothiing fancier. 

Multimeter can measure the 5V voltage on gpio header (https://www.raspberrypi.org/documentation/usage/gpio/)
but it will be below 5V when kodi is busy (technically it is instantaneously below 4.6V for the warning symbol to appear, but you may not see that on a multimeter).

This is a known good supply: https://www.raspberrypi.org/products/ras...er-supply/

Unfortunately a lot of power supplies (especially cheap chargers) don't deliver the volts they claim under load. 

So it was indeed the power supply. A new one arrived today and all problems disappeared. My bad---I was under the mistaken assumption the the RPi 3 needed only 2A---possibly because my previous one was rated at 2A and apparently it went above and beyond until it died.

Thanks to everyone for their help.