The safety works precisely the same on the Shilen trigger as it does on the Walker trigger. If the safety does not cam the sear up sufficiently and the trigger is pulled while the safety is engaged, the rifle will fire when the safety is disengaged. This can occur due to wear, manufacturing variations, or a stock which has not enough clearance to allow the safety to engage fully. I have seen the same thing on numerous triggers which have a safety which operates in the same manner.
The thing to do is to investigate the problem , determine the cause, and take corrective action. If you are not qualified to do this yourself, you may entrust the job to one who is.
The alternative is to take a bunch of abuse from some of the know-it-alls on some forum and go from there. GD