Modifier shift do not work at to_if_canceled and to_if_invoked instructions

[HgKls]

The rule below for a US-Int'l keyboard maps a double click on 'A' into an 'Ä'. In the to_if_canceled and to_if_invoked’ instructions, "key_code": "a", "modifiers": ["shift"] do not work, i.e. the modifier ‘shift’ is not sent, so that an 'a' is output instead of 'A'.
This misbehaviour is best seen if the parameter basic.to_delayed_action_delay_milliseconds is set to 2000 or higher.
Karabiner-Elements version: 15.3.13

{
    "description": "Ä if double-click on 'A' key (250ms)",
    "manipulators": [
        {
            "conditions": [
                {
                    "name": "A_pressed",
                    "type": "variable_if",
                    "value": true
                }
            ],
            "from": {
                "key_code": "a",
                "modifiers": { "mandatory": ["shift"] }
            },
            "to": [
                {
                    "set_variable": {
                        "name": "A_pressed",
                        "value": false
                    }
                },
                {
                    "key_code": "u",
                    "modifiers": ["right_option"]
                },
                {
                    "key_code": "a",
                    "modifiers": ["shift"]
                }
            ],
            "type": "basic"
        },
        {
            "from": {
                "key_code": "a",
                "modifiers": { "mandatory": ["shift"] }
            },
            "parameters": { "basic.to_delayed_action_delay_milliseconds": 250 },
            "to": [
                {
                    "set_variable": {
                        "name": "A_pressed",
                        "value": true
                    }
                }
            ],
            "to_delayed_action": {
                "to_if_canceled": [
                    {
                        "conditions": [
                            {
                                "name": "A_pressed",
                                "type": "variable_if",
                                "value": true
                            }
                        ],
                        "key_code": "a",
                        "modifiers": ["shift"]
                    },
                    {
                        "set_variable": {
                            "name": "A_pressed",
                            "value": false
                        }
                    }
                ],
                "to_if_invoked": [
                    {
                        "conditions": [
                            {
                                "name": "A_pressed",
                                "type": "variable_if",
                                "value": true
                            }
                        ],
                        "key_code": "a",
                        "modifiers": ["shift"]
                    },
                    {
                        "set_variable": {
                            "name": "A_pressed",
                            "value": false
                        }
                    }
                ]
            },
            "type": "basic"
        }
    ]
}

[tekezo]

@HgKls Thank you for feedback!
I fixed this issue at v 15.3.14. Please confirm the latest beta version.