I've noticed something quite odd: at least two different people I know of do not receive my "share my drive" texts. One of them used to get them, but now does not (she uses an iPhone). The other person uses a feature phone. The majority of people I've sent them to get them. I know something is definitely funky though because I tried sending several in a row from Waze along with regular texts, and the regulars get through while the Waze ones did not.
On a slightly related note, is there a way to close all the windows that pop up at once? While sending a meet up text I can get 3 - 4 windows deep, and clicking the small 'x' or pressing back that many times while driving is dangerous.