We are a small manufacturing company that makes plastic tubing for medical devices. We are not the finished product and we hold our cert ISO13485.We received 2 customer complaints that the 2nd outer bag was not there. 2 different employees, and 2 different shifts. The employee missed 6bags that are required by the customer double bagging. I have been here very short time. I notice that they really never address there complaints with solutions just making excuses and leaving the door open for re-occurrence. All final packaging is done in a CLEAN ROOM area but really isn't but its cut off from the production areas. We do order clean room plastic tubing bags that come on rolls and we cut to what ever length of tubing needs packaging. Mind you customer requires the inner bag to be labeled. Then when you get the 2nd bag on sometimes its hard to tell that its there without man handle some of the more sensitive tubing. My question is I am looking for some suggestions on how to mistake proof this besides going to each employee and reminding them to do this. I will also say I cant change the color of the bags either. I am racking my brain out to come of with a simple solution where I'm not adding another step where it still could be missed. Oh yeah I also looked into having the company logo on the outer bag but its not going to work because we cut to desire length.
Thanks for any and all feed back. I really need help with this.

Thanks for any and all feed back. I really need help with this.