Noticed a similar issue with a Dahua HFW-5442E-Z4E-S2 (8-32mm zoom) camera. When a vehicle would come across the field of view the image would bloom and return to normal brightness when the vehicle was gone.
This camera is using the shutter set for 'customized range'. Setting were 0 - 6 for the shutter and gain 0 - 40. Also noticed that the shutter settings had the greatest effect on the blooming image.
New settings that solved the issue for daytime:
Shutter 6 - 10
Gain 0 - 65
No nighttime data available at this time.
Note: gain was increased to make up for loss of shutter range.
In my case, if the shutter was set at 4 - 10 (1/250 sec - 1/100 sec) then the issue would again be present, but at 6 - 10 it would not. The slower shutter at 10 (1/100 sec) did not effect the issue. But at 4 (1/250 sec) the faster shutter speed did.
Overall, try changing the faster shutter to one that is slower and see if this will change your outcome. Even 6 - 6 could work but maybe too limited in range for your application. i.e. basically a fixed shutter speed.
Update
Another contributing factor is the setting for "Exposure Comp". If set too high the blooming will once again appear as evening approaches (less light).
Noticed that a setting above 10 would exacerbate the issue. Thus have settled on a setting of 6 for "Exposure Comp".
When "Exposure Comp" is reduced, the image may become too dark. One fix is to increase "Iris". In this example the setting was 19 and was increased to 29.
This is an isolated issue as other Dahua cameras all perform without this problem. This one camera, because of the FOV and lighting conditions requires this special setup.
Exposure settings currently in use for day mode are:
Shutter: 6 - 10
Gain: 0 - 75
Iris: 29
Exposure Comp: 6
Advanced 3D: 20
Advanced 2D: 0