Version 7.4.0.161
I'll assume you are using the legacy backup format. You created an image backups to a NAS that chains an image backup to the cloud. You are doing this so one plan can follow the other without the risk of overlap and a possible backup failure.
As I recall from these changes some time back, the previous implementation was flawed in that the chained backup could only ever run an incremental backup (or you could force a full - but that was not a great option). Since you are running image backups, then you need to periodically run a new full or you end of with a very long incremental backup chain and a risk of data loss if any incremental backup in the chain is lost / damaged.
The change, though, is as you describe. Either the chained backup follows what the parent backup plan does (meaning, a full for a full, an incremental for an incremental) or you force a full (which again is not a great option for most customers).
I am not exactly clear how the old implementation was working for you given that the chained plan always ran an incremental backup, which as I explained earlier is risky.
You could:
1- Continue to use the legacy backup format and use a Hybrid backup. A hybrid backup reads the source data once and sends it to two locations: a local target (your NAS) and cloud storage.
2 - Continue to use the legacy backup plans as you have them now, but do not chain them. Instead, schedule their periodic full backups on different days (use a synthetic full on the cloud backup if the option is available) to avoid overlap and schedule incremental backups as well to avoid as best as possible overlapping times.