Data Replication REDO rate very low on read-able secondary

Question

I am currently running MS SQL Server 2016 with 1 primary replicating to 1 synchronous node and 4 asynchronous nodes (1 in same data center, 3 in a failover data center).

My current problem is that my read-able secondary in our primary data center is showing a REDO rate of 25k kb/s, where as all my other nodes (including the other read-able secondary) is showing 120k-250k kb/s REDO rate. So the issue I'm running into is when a large data sync or index rebuild happens is I'll get a 40GB log file where the send rate is wonderful and everything is hardened in the log within minutes. But the REDO rate is taking upwards of hours sometimes to commit it all on the one node.

The only difference I can see on this node is that we have SSAS and SSIS services installed on this node however, no traffic to either of those systems during these large transfers. I am curious if anyone knows anything about whether it's sharing REDO rate between SSAS, SSIS & SQL Server and that is where my issue is. Only way I can really test is shutting down those services right now and since it's a production system I'd rather not be doing that if I can avoid it.

Wondering if anyone has seen an issue similar where one of their nodes were getting much lower than expected REDO rates and how you went about fixing it?