iPhone SE 2020 GPS speed on apps is very laggy

Since updating to iOS 16.7 and then to 17 (to see if that solved the problem) there is a definite and very noticeable lag between actual speed shown on Waze navigation app screen in the car and the actual speed the car is travelling. 

This is a new problem, prior to recently, the speed shown on Waze and on the car have been aligned and consistent. Eg as car accelerates, speed on waze rapidly increases in line with car. And same when it decelerates.

Same issue occurs when checking speed on Speedbox app. Which indicates to me that its an iOS problem with these versions running on a SE 2020 phone.

For example, accelerating from stopped, the car reaches the speed shown on the speedometer, yet Waze speed is slow to catch up to show the corresponding speed. The same happens the other way - slow the car down to a stop, and it takes the speed readout on Waze 4-5 seconds to get down to zero, and sometimes it stays showing 1km/hr.

So a definite lag between reality and what Waze is showing. Has not been like this before. Its as though the GPS update rate has slowed or been smoothed dramatically.

Also when driving at a steady speed, even with the car on cruise control, when the Waze speed actually catches up to the cars speedometer and steadies, there are sudden fluctuations in the speed displayed on Waze. For example I was cruising at a steady 60km/hr and Waze jumped to 19km/hr then back to 57 then jumped to 29km/hr and back to 55 then slowly up to 60. 

So it seems to me to be an issue to do with GPS update rates or how the GPS signal is processed. I run advanced GPS systems in my boat so I do have some understanding of GPS.

To further test, I connected my phone to a friends Toyota Landcruiser and it did the same thing. Laggy speed data.  By contrast, his SE2022 did not have any noticeable lag.