Worth emphasizing is that this isn’t a widespread bug, but it’s happening on more than a handful of devices, so it’s definitely something that needs to be investigated by the Google Maps team.
For example, someone on Google’s forums notes that the first few words that Google Maps says whenever it needs to provide navigation directions are always clipped. This only happens when the Bluetooth connection is being used and after the latest app updates that were published in the App Store. Several other users confirmed that the same thing happened on their devices too.
Then, someone else explains that the voice navigation is cut off, with the first few words never actually spoken.
“For the past 2 weeks or so, when Google Maps gives me the voice navigation over Bluetooth (as phone call as always), the first 2 seconds aren't voiced. So if the directions are supposed to be ‘Continue straight on Main Street for 3 miles’, what I hear is ‘...on Main Street for 3 miles’, the first few words are cut off,” one user explains.
Of course, the typical workarounds that are available on the iPhone, and which involve things like re-installing the apps, don’t make any difference. Due to Apple’s restrictions, users are not allowed to install an older version of Google Maps, so at this point, it’s rather hard to determine if the latest app release is the culprit or not.
When used without a Bluetooth connection, with voice navigation going through the phone speakers, everything appears to be working just fine, with all words spoken correctly whatsoever.