.send_keys("x.x") for iOS slider is not working

Hi all,
I’m trying to automate slider in iOS app. I want to move it via send_keys …it looks it is ok but in device (real device) it doesn’t move. I also tried all possible input methods but didn’t help. I also tried to add the value like “50%” …didn’t help
my code:

@driver.find_element(:predicate, “type == ‘XCUIElementTypeSlider’ AND visible == true”).send_keys(“0.5”)

info:
iPhone 8 Plus
ios: 11.4.1
Appium: 1.9.0

the slider:
Attribute Value
type: XCUIElementTypeSlider
value: 0 %
enabled: true
visible: true

appium logs:
2018-10-16 13:34:24:269 - [HTTP] --> POST /wd/hub/session/f9f4b425-a4f9-4022-98ae-e4ce95bbf406/element
2018-10-16 13:34:24:269 - [HTTP] {“using”:"-ios predicate string",“value”:“type == ‘XCUIElementTypeSlider’ AND visible == true”}
2018-10-16 13:34:24:270 - [debug] [W3C] Calling AppiumDriver.findElement() with args: ["-ios predicate string",“type == ‘XCUIElementTypeSlider’ AND visible == true”,“f9f4b425-a4f9-4022-98ae-e4ce95bbf406”]
2018-10-16 13:34:24:270 - [debug] [XCUITest] Executing command ‘findElement’
2018-10-16 13:34:24:272 - [debug] [BaseDriver] Valid locator strategies for this request: xpath, id, name, class name, -ios predicate string, -ios class chain, accessibility id
2018-10-16 13:34:24:272 - [debug] [BaseDriver] Waiting up to 20000 ms for condition
2018-10-16 13:34:24:273 - [debug] [JSONWP Proxy] Matched ‘/element’ to command name ‘findElement’
2018-10-16 13:34:24:273 - [debug] [JSONWP Proxy] Proxying [POST /element] to [POST http://localhost:8105/session/1CB2F250-2B96-4CDA-B9E8-E06735A78F11/element] with body: {“using”:“predicate string”,“value”:“type == ‘XCUIElementTypeSlider’ AND visible == true”}
2018-10-16 13:34:24:647 - [debug] [JSONWP Proxy] Got response with status 200: {“value”:{“ELEMENT”:“5F000000-0000-0000-B501-000000000000”},“sessionId”:“1CB2F250-2B96-4CDA-B9E8-E06735A78F11”,“status”:0}
2018-10-16 13:34:24:648 - [debug] [MJSONWP] Responding to client with driver.findElement() result: {“ELEMENT”:“5F000000-0000-0000-B501-000000000000”}
2018-10-16 13:34:24:649 - [HTTP] <-- POST /wd/hub/session/f9f4b425-a4f9-4022-98ae-e4ce95bbf406/element 200 379 ms - 122
2018-10-16 13:34:24:649 - [HTTP]
2018-10-16 13:34:24:654 - [HTTP] --> POST /wd/hub/session/f9f4b425-a4f9-4022-98ae-e4ce95bbf406/element/5F000000-0000-0000-B501-000000000000/value
2018-10-16 13:34:24:654 - [HTTP] {“value”:[“0.5”]}
2018-10-16 13:34:24:654 - [debug] [W3C] Calling AppiumDriver.setValue() with args: [[“0.5”],“5F000000-0000-0000-B501-000000000000”,“f9f4b425-a4f9-4022-98ae-e4ce95bbf406”]
2018-10-16 13:34:24:654 - [debug] [XCUITest] Executing command ‘setValue’
2018-10-16 13:34:24:657 - [debug] [JSONWP Proxy] Matched ‘/element/5F000000-0000-0000-B501-000000000000/value’ to command name ‘setValue’
2018-10-16 13:34:24:657 - [debug] [JSONWP Proxy] Proxying [POST /element/5F000000-0000-0000-B501-000000000000/value] to [POST http://localhost:8105/session/1CB2F250-2B96-4CDA-B9E8-E06735A78F11/element/5F000000-0000-0000-B501-000000000000/value] with body: {“value”:[“0”,".",“5”]}
2018-10-16 13:34:25:017 - [debug] [JSONWP Proxy] Got response with status 200: {“value”:{},“sessionId”:“1CB2F250-2B96-4CDA-B9E8-E06735A78F11”,“status”:0}
2018-10-16 13:34:25:018 - [debug] [MJSONWP] Responding to client with driver.setValue() result: null
2018-10-16 13:34:25:018 - [HTTP] <-- POST /wd/hub/session/f9f4b425-a4f9-4022-98ae-e4ce95bbf406/element/5F000000-0000-0000-B501-000000000000/value 200 364 ms - 76
2018-10-16 13:34:25:018 - [HTTP]

Any advice would be really appreciated

For brightness in Settings it is working. So probably it is the slider in the app making problems…