Losing icons (shortcut and sometimes program) from programs in taskbar group

I wanted a group on the taskbar for system functions and utilities. There are too many that I use regularly and they'd fill the taskbar. I want a clean desktop and don't like having stuff pinned in the start menu. So...

To do that, you put all the shortcuts you want in a folder somewhere. You then define a shortcut with the target as "explorer.exe c:\path to folder with shortcuts". Pin that shortcut to the taskbar and you've got a taskbar group. CIick it and you get an explorer window open to your shortcut folder.

About 4 or 5 days ago, I got tired of the regular old folder icon for the group and downloaded one that looks like a laptop. This may or may not be related to what's happening.

Yesterday, when I clicked on the group icon, one shortcut had lost its icon, reverting to a generic blank shortcut icon. Today, it's seven of them. If you go to the target folder in Program Files, File Explorer also shows a blank icon for the program itself. Open properties for the program, and the header still shows the correct icon. Open the program and it shows the correct icon at the top left of its window. Open properties for the icon and click "change icon" and it shows the correct icon. Selecting it and hitting Apply or OK sometimes doesn't change it until the 2nd try. Double clicking the desired icon almost always works on the first try.

The whole icon mess is odd and a PITA to recover, especially if it's going to be a frequent thing. Even so, I don't want to abandon the group, and I'm resisting going to a 3rd party taskbar customization program.

I'm tempted, of course, to revert to the old folder icon for the group. But how in the world is this happening?

rebuild your icon cache

Update - I've gone into properties for all the shortcuts that lost their icons and fixed them, except one. Ookla Speedtest was an install from the MS Store and isn't easy to find. Not in Program Files. Then, I deleted and remade the shortcut to the icon directory, this time with a generic icon from Shell32.dll. Finally, I deleted (gone, not to Recycle Bin) the downloaded icon that I'd used previously for the group. Let's give it a couple of days and some boots to see what happens.

If it's still acting up, then I'll try rebuilding the icon cache, per @glasskuter post.

For Store apps, look in shell:appsfolder

You can open that form the Run dialog, or by simply typing it in the address bar in an open Windows Explorer window.

As for the icons going wonky - did you save the icon image file to either your Pictures / Documents folder? And if so, is that folder shared via OneDrive? If so, is OneDrive set to remvoe files that ahven't been used in a while to save local storage space?

If so, a couple of possible fixes:

1) Set that file to be always available offline in OneDrive
2) Save the file in a location that is not shared to OneDrive

@johnlgalt
OneDrive is disabled. The downloaded icon was saved in a local directory. It's not the one that went missing. Those were the utilities.

I'll check the location for Ookla when I get back home to the computer.

Thanks!

As for Ookla Speedtest I use the online link, it offers several not too far away but can choose a different city.

I've followed @glasskuter 's suggestion and rebuilt my icon cache using the BAT file from the tutorial. Now giving it a couple of days and some boots to see if everything is happy again in icon-land.