Trouble with gif loading in Android

[Semstep]

Hi!
There are pictures in png and gif, which should be displayed on top of buttons, and I am confused with this.
Both buttons are described the same, only the types of pictures are different. There was png, but now I want gif in one of the button.
It works good in Windows, but in Android I can see png, white square instead of gif and 'image.py | 276 |    ERROR | Image: Error loading <assets/restart.gif>  in my log
What am I doing wrong?
And the second question. When shoud I have to do 'buildozer appclean'?
Thanks!

Button:
id: status_
size_hint_x: None
width: self.height
on_release: app.root.controller.act_restart()
Image:
source: './assets/restart.gif'  # There is ./assets/help_icon.png in another button and works fine
center_x: appstatus.center_x
center_y: appstatus.center_y
size: status_.size
allow_stretch: True
keep_ratio: False

Corresponding part of buildozer.spec:

# (str) Source code where the main.py live
source.dir = .

# (list) Source files to include (let empty to include all the files)
source.include_exts = py,png,jpg,gif,kv,atlas,yml

# (list) List of inclusions using pattern matching
source.include_patterns = assets/*,Controller/*,Model/*,Utility/*,View/*,Logger/*

# (list) Source files to exclude (let empty to not exclude anything)
#source.exclude_exts = spec

# (list) List of directory to exclude (let empty to not exclude anything)
source.exclude_dirs = tests, bin, venv, .git, .idea

# (list) List of exclusions using pattern matching
# Do not prefix with './'
#source.exclude_patterns = license,images/*/*.jpg

# (str) Application versioning (method 1)
# version = 0.101

# (str) Application versioning (method 2)
version.regex = __version__ = ['"](.*)['"]
version.filename = %(source.dir)s/main.py

# (list) Application requirements
# comma separated e.g. requirements = sqlite3,kivy
requirements = python3,kivy,plyer,pyyaml

[Robert]

The second question: https://github.com/Android-for-Python/Android-for-Python-Users#changing-buildozerspec