sparsebundle reverting to read-only
As far as I have understood, macOS allows read-only mounting sparsebundles in almost all situations.

However, when you want to read/write mount a sparsebundle, the underlying filesystem (in this case the network protocol you're using for mounting the wireless drive - for example AFP or SMB) must support F_FULLFSYNC. If your system does not support that the risk of data loss is substantial.

Therefore check if you can use a different protocol, or you can change the settings, mount options or FUSE-driver (if such is used) to allow F_FULLFSYNC.