El Capitan and gmail

Hi AppleVis users, I wonder if anyone here can shed light on a situation I have experienced several times now. I have a MacBook Air running OS X El Capitan. Whenever I attempt to compose a new email by way of gmail.com instead of the computer's native mail app, the VoiceOver cursor starts acting strangely. If I am in the message text entry field, at random intervals the VO cursor jumps to the beginning of the block of text I just entered. Words often get cut in half this way, and I have to delete the characters at the top of the message, then move the cursor back to the bottom in order to continue. It isn't a huge problem, but annoying as anything. Is this a bug, or are there settings I can change to stop it? Apologies if this issue has been brought up in the past, I couldn't find the forum topic.