Each time I open LRTL with a new sequence it ALWAYS opens old project sequences that do not even exist on the HDD. How to avoid this...

LRTimelapse only shows folders, that DO exist. There is no catalog or similar - just your folder structure.
So I don't know exactly what you mean with "old projects" - could you please explain? Maybe with a screenshot?

I use a 100CANON folder on my edit raid. After I end editing a project-sequence I erase everything from the HDD. Next project sequence I load the same folder from the SDCard (copy to disks for faster processing). After opening LRTL and inspecting the folder it loads the previous sequence that does not exist, erased from trash. I do not find somewhere a key to update the folder so I can see on preview the new sequence of images or delete the old one..... I need to close LRTL, change the name of the folder and then on the next LRTL opening then it recognises the new folder and new sequence. Hope I am clear now.
Thanks