ModeController.mode - "device doesn't support that"

My issue: After enabling Alexa smart skill control for my new Daikin air condition Alexa service responses “device doesn’t support that” when I request the mode “AUTO”:
Alexa command: “Stelle Klima Schlafzimmer Modus auf Automatik” – “set air condition bedroom mode to automatic”. Alexa response: “Klima Schlafzimmer unterstützt das nicht” – “air condition bedroom doesn’t support that“

Item configuration (related to the issue):

Group  DaikinACUnit_Bedroom	"Klima Schlafzimmer"											{ alexa="Endpoint.Thermostat" }
Switch DaikinACUnit1_Power	"Power [MAP(de.map):%s]"	<switch>	(DaikinACUnit_Bedroom)	{ channel="daikin:ac_unit:192_168_2_140:power",		alexa="PowerController.powerState" }
String DaikinACUnit1_Mode	"Modus []"					<heating>	(DaikinACUnit_Bedroom)	{ channel="daikin:ac_unit:192_168_2_140:mode",		alexa="ModeController.mode" [supportedModes="HEAT=Wärmen:Warm,COLD=Kühlen:Kalt,AUTO=@Setting.Auto,DEHUMIDIFIER=Trocknen,FAN=Lüften",friendlyNames="Modus"] }
//String DaikinACUnit1_Mode	"Modus []"					<heating>	(DaikinACUnit_Bedroom)	{ channel="daikin:ac_unit:192_168_2_140:mode",		alexa="ThermostatController.thermostatMode" [binding="daikin"] }
String DaikinACUnit1_Fan	"Lüfterstärke []"			<fan>		(DaikinACUnit_Bedroom)	{ channel="daikin:ac_unit:192_168_2_140:fanspeed",	alexa="ModeController.mode" [supportedModes="SILENCE=Leise,LEVEL_1=Eins,LEVEL_2=Zwei,LEVEL_3=Drei,LEVEL_4=Vier,LEVEL_5=Fünf,AUTO=@Setting.Auto",friendlyNames="Lüfter stärke, Lüfterstärke"]}

Detailed explanation:
The issue occurs with item DaikinACUnit1_Mode (with item DaikinACUnit1_Fan same issue). All other modes for this item I configured with ModeController interface are working properly, except mode “AUTO”. I tried i.a. with supportedModes “AUTO=@Setting.Auto”, “AUTO=Auto”, “AUTO =Automatik”, “AUTO=Steuerung” using corresponding alexa commands. Nevertheless, when I set device to mode “Automatic” manually with remote control or via Basic UI then item DaikinACUnit1_Mode gets the value AUTO – i.e. this value is valid.
In desperation I tried ThermostatController interface using property thermostatMode (see item configuration – commented out) but modes DEHUMIDIFIER and FAN are not supported by Alexa. When one of those modes is selected (via remote control) and I ask Alexa “Wie ist der Modus von Klima Schlafzimmer?” (“What is the mode of air condition?”) the ‘full’ answer is “Unterstützt das nicht” (“Doesn’t support that").

OpenHAB configuration: OH 2.5.0.M4 Milestone Build, Daikin Binding Snapshot 2.5.9.202009190345

Workaround with two items pointing to the the same thing channel using Alexa ThermostatController interface in combination with ModeController interface worked for me:

Group  DaikinACUnit_Bedroom	"Klima Schlafzimmer"											{ alexa="Endpoint.Thermostat" }
Switch DaikinACUnit1_Power	"Power [MAP(de.map):%s]"	<switch>	(DaikinACUnit_Bedroom)	{ channel="daikin:ac_unit:192_168_2_140:power",	alexa="PowerController.powerState" }
String DaikinACUnit1_Mode	"Modus"						<heating>	(DaikinACUnit_Bedroom)	{ channel="daikin:ac_unit:192_168_2_140:mode",	alexa="ThermostatController.thermostatMode" [binding="daikin"] }
String DaikinACUnit1_Mode2	"Modus 2"								(DaikinACUnit_Bedroom)	{ channel="daikin:ac_unit:192_168_2_140:mode",	alexa="ModeController.mode" [supportedModes="DEHUMIDIFIER=Trocknen,FAN=Lüften",friendlyNames="Modus"] }