Stuck in gear when coming to a stop.

Hi all.

I bought my 2002 NBFL 1.6 MX5 a few months back. It's been driving fine since I bought it. The other day I pulled up to a junction and put my car into first gear. When I came to a stop I left off the brake and as I did (Clutch to the floor still) my car pulled away as if the clutch was still engaged. I pressed on the brake again to stop myself rolling into live traffic. Still confused I let off the brake thinking the car was rolling and I was over thinking things but it did it again. It was pulling away so I let up the clutch and added gas to prevent a stall. When I let off the clutch it had no resistance. Once I was moving the car drove as normal. The clutch pedal felt fine switching through the gears. I got home fine with no more faults so I figured it was time to start saving for a new clutch. Earlier today the fault happened again in a very similar fashion. It only occurs when I stopped the car and balanced the clutch. It wont let me change gear even if I power down the car. The clutch pedal gets no resistance and I have to pump the clutch to disengage the gear I'm in. I've tested it and the same happens no matter what gear I'm in. Could really use some help figuring this one out as I can't find much if anything on the topic. I've got a suspicion it's to do with master or slave cylinder or maybe just air in with the fluid as I've yet to change it. The fluid quality is poor but full and no visible leaks or damage to either cylinder. When I first bought the car I rebuilt the shifter and used a turkey baster to replace the fluid in the transmission.

Has anyone else had this issue or know what might be the cause?