Template matching returns "Resizer: image is locked"

Hello,
Using FIJI, I convert my 8-bit grayscale image to RGB, then I draw a ROI and try to run the template matching but it returns the following error.
<<Resizer: image is locked (img["sample_image.tif" (-4), 24-bit, 672x512x1x1x1])>>
I tried (Plugins->Utilities->Reset...->Locked image) that returns that the image is now unlocked but still it fails with the same error, whatever the image.