If it’s always slow then your InReach sounds like it is faulty. Probably deaf due to defective antenna connections, static damage to receiver front end active devices, inability to maintain network sync due to gross timing issues.
My own Iridium device has failed to uplink twice out of several hundred messages sent. Once was in 75% partial tree cover shown below and I expected issues with it in that location.
The only other time was when I was in a remote part of Northern Scotland and despite gaining sync the message failed to send. I waited a few minutes and tried again (there is a default time lockout on failed uplinks when my device wont send anyway). This time it worked. It’s possible, as Iridium uplink is to a single satellite, that my body moved into the view the device had of the satellite in the sky attenuating the signal. As GPS uses data from multiple satellites, you are less likely to obscure all the satellites with your body.
Usual time from send pressed to spot appearing on SOTAwatch for me is under 30secs including the uplink to Iridium satellite, transfer via sats to sat nearest Iridium downlink station, downlink itself, internet propagation to server, posting to SOTAwatch.