Flashing Indicator's

Probably the wrong rating, so that they're not compatible with the flasher relay.

Have you replaced them with LED bulbs? If so are they CANBUS bulbs or not?

Wrong bulbs..stick to originals unless your positive they will work.

Could be inadequate inadequate earthing, though this usually manifests itself by all lights fluctuating in that particular light array. The new bulbs draw more power and the earthing is not increased so its not matched.

Or the other thing is are all your indicators working OK? If one of them is not working (check side repeaters and, if if you have them, mirror lights).

No answers but reminds me of the time, many years ago, I put the wrong brake light bulb in my car and every time I pressed the brake pedal my headlights flashed, didn't realise for ages.

Highly likely the problematic items do not have similar resistance to original bulbs and so confuses the flasher unit that controls the flash rate based on the current flowing through the bimetallic-strip inside the flasher unit. Add some external resistance (not for the faint-hearted unless you can buy a kit suitable for your application) or return to original bulbs.

Can I just change the flasher relay ..?

tarr48 m ago

Can I just change the flasher relay ..?

It may help if you told us what the original bulbs were and what you have replaced them with, it’s ok saying brighter and more energy efficient but that’s not telling us the type and spec of bulbs.

15SMD 2835 high bright LED
Base type
1156 BA15S
approx 500 lum
12V DC
White(5500K )
-Quick to start
-Canbus Error Free
These are the current led I am using
These are the original bulbs
lucas LLB382 Ba15s SCC tail light
12v 21W ECE

There's your problem, you can't just swap out standard bulbs for led ones, as the resistance will be different thus causing problems with the flasher relay, if you have the original bulbs still just swap them back to see if they work okay.
If you want to persist with the new bulbs you have you'll need to find a competent auto electrician who can check the resistance and then wire in a new resistor to compensate for the new bulbs.
Edit: does it state how many watts the new bulbs draw as this will help determine what you need to add to the circuit to compensate.

tarr32 m ago

15SMD 2835 high bright LEDBase type1156 BA15Sapprox 500 lum12V …15SMD 2835 high bright LEDBase type1156 BA15Sapprox 500 lum12V DCWhite(5500K )-Quick to start-Canbus Error FreeThese are the current led I am using These are the original bulbs lucas LLB382 Ba15s SCC tail light 12v 21W ECERead lessRead more

You will need to install load resistors, if you are unsure how to do so either an auto electrician or YouTube would be a great start.

Thanks