Possibly the device takes more time to charge due to some dirt on the band contacts or the pins of the charging dock.
So first, please check the band contacts. If you find dirt or black dots on the band contacts, please try cleaning them.
For cleaning, you will need table vinegar with a concentration of no more than 10% and a cotton swab.
Dip a cotton swab into a small amount of vinegar
Soak the contacts in vinegar and leave them like that for 10 minutes, ensuring that the vinegar doesn't dry out
Rinse the contacts under running water while still rubbing the contacts with a cotton swab
Rinse the contacts again under running water without using the cotton swab this time
Dry the band with a tissue and remove moisture from the charging contacts by using a dry cotton swab
Next, please check the pins of the charging dock. If you press the contacts on the charging dock and they have difficulty returning to its original position, please check if there is clogged dirt or dust around them and remove it.