SRC HK416 semi auto firing issue and slow auto rate of fire

[maslin4863]

I decided recently to get a second hand AEG as a back up for when I don't fancy using my GBBRs or unable to but am having a few issues and after some advice on if anyone has had similar problems and a rough idea of how much it may cost to sort out?

The first issue is the AEG seems to struggle to cycle the piston to fire a bb in semi automatic, it takes about four pulls of the trigger to fire a single bb successfully? When I removed the receiver to see if it was working i tried pulling the trigger to see what was happening and could see that when I pulled the trigger the spring would compress a little, then on the second pull a little more, then a little bit again before firing?

The second issue is when it is set to automatic it fires bb's but it cycles very slowly and I could probably fire faster on semi automatic........if it worked that is!

Has anyone ever had similar experiences and have a rough idea of what could be causing the issues?