Paint bucket acts "weird"

[PieterJW]

GIMP 3.0.6 on Linux Mint 21.3 Cinnamon
Using the paint bucket tool, sections that were already filled change color.
I made an image with several sections that I want to fill with the paint bucket. 
I filled several sections with red without a problem.
I start filling the next sections with pink (see settings below) When I fill the first empty section with pink, no problem. When I click the second empty section, it is filled with pink, but the first pink section changes to red. When I click the third section, the second changes to red as well. When I click the second section again, that one turns pink but the third one goes to red.
The sections are closed; there's no "leakage".
I tried closing and restarting the program, but that didn't change anything.

I hope this description makes sense. I wanted to attach a video but that didn't work.

Does anybody know why this happens and - more importantly - how to prevent this?

Foreground color: pink
Background color: white 
Tool settings:
FG color: pink
BG color: white
Mode: normal
Fill type: FG color fill
Affected area: fill similar colors
Finding similar colors: Fill transparent areas
Threshold: 116,1
Fill by: composite

Thank you.

[rich2005]

Is the Image in Indexed Mode ? ie. What does Image -> Mode show. If it is Indexed, then  change to RGB

Otherwise
Post a screenshot of your whole gimp interface showing layers and tool options as well as any active selections.

EDIT: Starting to guess about your image but if the shapes are on separate transparent layers then lock the alpha channel before filling. A quick example https://sendvid.com/b9mbddww

[PieterJW]

(4 hours ago)rich2005 Wrote: Is the Image in Indexed Mode ? ie. What does Image -> Mode show. If it is Indexed, then  change to RGB

Otherwise
Post a screenshot of your whole gimp interface showing layers and tool options as well as any active selections.

EDIT: Starting to guess about your image but if the shapes are on separate transparent layers then lock the alpha channel before filling.  A quick example https://sendvid.com/b9mbddww

Thanks for your reply.
Image is in RGB mode.
The shapes are on one transparent layer.
The screenshot is attached.