I have an odd question. My phone is a SPA514G and has a SPA500S sidecar attachment with 25 transfer lines programmed into it, so when I want to transfer a call I just hit the button belonging to whichever phone the call should go to and then hang up my phone. Most of the time, these transfers work fine, but probably 5-10% of calls get "lost". I'll hit the button on the sidecar to transfer them, and then... nothing. They don't get transferred but I can't get back on the line with them. It opens up my second line as if the caller is on hold on the other but I can't get back to them. My coworkers have this happen to them occasionally but as I do most of the transfers it's much more noticeable on my phone. Is there any way to fix this, or is this an issue that's known to happen with these models?