Glitch with gradient tool. It keeps stacking and doesn't allow to relocate nor change opacity

Bracketed images, one on top of the other in the form of layers > generate layer mask > in order to reveal detail from the image underneath I have always used a radial gradient to start slowing working in detail. Seems to all of a sudden have a glitch and if I move that radial gradient around it actually starts stacking and the opacity control no longer has an effect (it is from black to transparent)