When you let go of the mouse button, the object should stop moving. If that doesn't happen, I would probably suspect the mouse. Are you using a graphics tablet?
The only way I could see this happening, is maybe if you have locked a layer. Although if that were the case, you would not be able to pick it up either. I can't think of any way that you could have picked it up from an active layer, and brought it to a locked layer. If that were the case, it would likely be a bug.
You're welcome to share the SVG file, if you want us to look at it. But I might be the only one who can look at it. Most everyone else has moved to the new forum. Read on.
Apparently you can't see the announcement on the forum index page, that this forum is not taking support questions anymore, and will be shut down completely in a little over a month.
There's a new forum on the Inkscape website. There are lots of people there who can help, while there are very few people here.
https://inkscape.org/forums/
