My HW27KS does this when raising & lowering. There's a thread on here somewhere discussing it as it's quite common. Mine is the telescoping lifting posts, I think there are 2 or 3 sections to it, it's like a section will start to raise but there's nothing to hold it in place yet, so slides back down. I have actually watched one of mine do it, scares the hell out of me each time it 'bangs'
Someone suggested putting some dry lube on the inside of the posts, I haven't done it yet but plan to.
2018 Flagstaff HW27ks
2015 Jeep Grand Cherokee Overland