My Myvi SE also like that. They got screw at the bottom and side only.... top use double side tape one.
The problem about 1 week after i get the car but i got no time to repair it immediately.
I complaint during my first service.
Recently after 9 time there only now fix..... waste so much time at SC.

First service - complaint but they say cannot fix then, too busy.. need to make another appointment
2nd visit - go there for about 2 hour plus only to remove it... they say need time to clean the double side tape
3rd visit - go to put back the side skirting. Seem ok there, reach home the gap come out again.
4th visit - arrange another visit to SC after phone complaint, remove it and they claim another skirting for me
5th visit - go to put back the new claimed skirting. There seem ok, but the gap again after 1 days
6th visit - go AGAIN to remove the skirting .....need time to clean the doubleside tape
7th visit - go to put back the skirting AGAIN.... say use better quality double side tape..... after waiting for 3 hours... they say sorry.. the skirting seem curve already... so... how they put it also got gap.. so take picture and claim for new skirting AGAIN....
8th visit - week after raya go to put back the newly claim skirting AGAIN... then they say sorry.. forgot to call me.. their subcontractor not yet back from raya.. skirting is there... not painted yet... WTF
9th visit - SC like my second home already.... sien.... waited for another 3 hour... finally finish.. until today... about 1 week plus... seem ok lah

Who say perodua service very good one... i spend like 3 hour every visit.... between visit usually a week or more cause i only free at saturday....
total spend for that stupid plastic skirting is about 27 hour already..... by the way, the SC is Keramat one... my second service i go other place already....

They claim that the side skirting not straight enough, therefore it will have gap at one end.. but i suspect it's just their workmanship lah...... how hard is there to put a side skirting.. not like any major engine damage, anyway i also lazy to discuss more with them, just glad can put this behind.