Thanks to all for your suggestions. Do you think it might help to put screws into the wall from the basement through the joist?
Do you think joist spacers or brackets might stabilize the flooring?
I have a new epoxy floor, which has dried. I now want to install a sliding closet door guide into the floor, by use of three screws. What is the best way to drill into the floor so i can use the screws? Thank you, from Wisconsin.