How to solve production / staff problems in a factory environment?

Lately where I work there have been huge problems with mistakes made during manufacturing. It’s not important what we produce, but they are bespoke, custom made products which are complex and varied. The staff are given very detailed drawings, and if they’re unsure what to do, there are people they can ask who will be able to tell them. They have all received adequate training so there’s no excuses there.

All sorts of things have been going wrong, from people forgetting to send components out with a delivery, general quality issues, people mis-reading paperwork, being inaccurate with measurements and other things.

It’s costing the company literally £1000s per month, and also costing it’s reputation with some of the customers who provide our company with the bulk of our work.

The management’s idea is to dock wages equal to the cost of correcting the problem (whether this is re-making components, sending people out to see customers, etc.) but I’m not sure if this is legal. Finding out if this is legal is not what I’m asking though, I was just wondering if anybody had any suggestions on good ways to solve issues like this.