Intermittent TX on Astro

[VSP5151]

I try to maintain a digital Quantar repeater and 20 Astro mobile radios. I had several units that would not always transmit through the repeater. About every 3rd transmission from these radios would not go through the repeater. I replaced these units with spares and now my unit is the only one that is intermittent. In addition to the company digital channels I have serveral analog amateur and GMRS channels in the radio and the analog channels never fail. I used the Astro software and performed all transmitter adjustments they described but my radio is still intermittent in the digital mode. Unfortunately the only service monitor I have is an IFR which does not decode C4FM. Any suggestions? I have one radio on the way to Motorola repair but intermittent radios are difficult to service.