External ssd caddy USB problems

I have a Macbook Pro 15" 2017 running Mojave and for several weeks now I've been having a problem with an external SSD in a caddy. It's a Salcar caddy with an LED that lights white for a USB 2.0 connection and blue for a USB 3.0 connection.

In the past the caddy would always light blue when plugged into a thunderbolt port on the Mac but these days it doesn't matter which of the four thunderbolt ports I use, the caddy lights white 90% of the time. I can sometimes get the LED to light blue if I put the plug into the Mac very slowly or halfway and if I slightly move that USB-C plug the LED usually turns white or sometimes disconnects (with error).

My point is that no matter which of the four thunderbolt ports I use they are all as temperamental as each other. I can only manage to get a USB 3.0 connection 10% of the time by re-plugging several times until it decides to give me a blue LED. Surely all four ports can't have become faulty at once? I've also tested the data transfer speed and the external caddy is transferring faster with a blue LED as expected.

I'm confused whether this is a problem with my Mac or the caddy electronics as it's behaving weirdly with all four ports.

Any help would be much appreciated.

Thanks in advance.