it happens to me using message+, the original text app, google messenger and on multiple phones. It happened on my galaxy s7, and now on my s9+ and on my other S9+ (first broke). It happens when I text alot at once. Sometimes it fixes itself when i go onto wifi, but less so now. It happens when I am using mms to text to multiple people. Then I can see when they send me text but I cant see what they say. The "download" appears individually from them but I cant download the message. I power on and power off. sometimes it fixes itself in an hour or so and I get a whole bunch of texts. sometimes if someone else sends me a text it then somehow releases others.
This has been going on for years and drives me insane. Any help woould be greatly appreciated