Tacx Neo Smart Bike - Left Hand Crank Arm Issue

The pedal has to be as close to possible to the bike. But after a few hours, it looses the grip and beginns to wiggle. I have build my own solution, the keep the pedals close to the bike. Look at my video: 

https://www.youtube.com/watch?v=jmwDTjJR3V0&t=2s

I have exactly the same issue on my bike - the left crank arm actually came completely off the other day, as I was riding (with my shoe still clipped to it!). Garmin is sending me a replacement kit for the crankset as a whole, but I wonder how long that will take. The through-bolt solution that Golf-VR6 describes sounds like by far the best way to prevent this ever happening again.

Get a metal crank cover from Amazon, the plastic *** garmin gives you will break.  

I had the same issue. The solution published by Golf_VR6 above helped temporarily, but not permanently. Then I finally came across the instructions published by Garmin. The clamping screw of the pedal must be tightened with a full 22 NM.

This solved the problem.
(German link: https://support.garmin.com/de-CH/?faq=qx9Oa6aRx11UiSQymAmR78&productID=690885&searchQuery=ger%C3%A4usche&tab=topics) 

I had the same issue. The solution published by Golf_VR6 above helped temporarily, but not permanently. Then I finally came across the instructions published by Garmin. The clamping screw of the pedal must be tightened with a full 22 NM.

This solved the problem.
(German link: https://support.garmin.com/de-CH/?faq=qx9Oa6aRx11UiSQymAmR78&productID=690885&searchQuery=ger%C3%A4usche&tab=topics) 

Hi ParlabaneDarcourt. Thanks for the link from Garmin, how to tightened with full 22 NM - maybe it helps. But, my solution is not temporarily, then I use the Taxc Neo Bike 2-3 times a week - and since over one year, I haven't had any problem with the crank arm :-)

In fact the metal continues to pop off the crank arm, I do have the bolts tightened to 22nm (I have a torque wrench). It does take a month or more for the cover to loosen. I am big at 6’5” and 220lbs. - riding around 150miles weekly so while not perfect the metal cover has allowed me to ride without to much worry. 

After my issues with the left crank arm, I bought a long bolt with self-locking nut and big "fender washers" that span the opening that the screw-in cap would cover. I had to cut off around 3/8" of threads in order to keep that end of the bolt from grazing my foot. However, with the long bolt in place and securely tightened, I have NO problems with the left crank arm loosening. 

When I opened up the mechanism to replace the freehub recently, then reassembled everything, I made a point of hunkering down rather hard on the through-bolt. This keeps the entire crank assembly nice and secure. 

I have the same problem , my bike is not fit to use, I can't find service in Portugal it's a problem. what crank should I buy? I need to buy both cranks?

Contact the Garmin support via Chat. Prepare before that a concise description, serial number (photo of the label on the bike), maybe videos with sound, … This helped me with several problems successfully. The service is outstanding! Using chat enables transferring photographs and videos, and gives Garmin time to check with their specialists. Yes, it takes time but both sides do not have to stay on the phone wasting time but can work on analysis and solutions.