There were some simple things this business could do, that many businesses could do, to improve this situation.
This business did have their processes documented, that is often issue number one for businesses who struggle in this manner.
The induction of staff could have included reference to the processes.
Simple flowcharts could be made available to give them a 'quick start' for getting their heads around the processes.
Skills matrices could be linked to the formal processes, to ensure that people know where to look to improve their knowledge.
Staff who 'help', by passing on their tips and notes, could do better by pushing them back into the induction process.
...and I am sure that you can think of more.
The training of your staff in your processes is a process in its own right. Hopefully you have mapped yours out. If you haven't then you have an opportunity to do so, and to develop the tools your business uses to re-direct and guide people so that learning your processes is consistent and not hap-hazard.
Author of Business Process Re-Engineering
P.S. For some further ideas on Standard Operating Procedures (SOPs) and embedding the knowledge in your business check out my book 'Effective SOPs':