DKIM Valid (Signed by DOMAIN.NAME) "Warning" Header 'Subject" is not signed

I have purchased on OVH a domain name and as part of it also comes with
FREE website plan called "100 MB free hosting"
and
E-Mail address with 1 account "Zimbra Starter e-mail account" service plan called "STARTER"
including 15 GiB space.

[DOMAIN.NAME = change to your domain name to check]

# WWW
After activating, both the "100 MB free hosting" &  "Zimbra Starter e-mail account"
I also activated "Secure delegation - DNSSEC" for the domain name purchased,
received e-mail from OVH with SFTP password link and other details.

"100 MB free hosting" also needed activating "SSL certificate" for naked and www subdomain
- DOMAIN.NAME | www.DOMAIN.NAME
and all works as it should.

[XXXXXXX = is a number before "jt.dkim.mail.ovh.net" in a CNAME record]

# E-Mail
For the "STARTER" - "Zimbra Starter e-mail account" I checked:

- and adjusted SPF - Sender Policy Framework
PERSONAL CHOICE:
[    600 IN TXT     "v=spf1 include:mx.ovh.com ~all"]
https://mxtoolbox.com/SuperTool.aspx?action=spf%3aDOMAIN.NAME#

spf:DOMAIN.NAME
spf:DOMAIN.NAME:all

- and added DMARC - Domain-based Message Authentication, Reporting, and Conformance
PERSONAL CHOICE:
[_dmarc        IN TXT     "v=DMARC1; p=reject; ruf=mailto:dmarc-ruf@DOMAIN.NAME; rua=mailto:dmarc-rua@DOMAIN.NAME; pct=100; adkim=s; aspf=s"]
https://mxtoolbox.com/SuperTool.aspx?action=dmarc%3aDOMAIN.NAME#

dmarc:DOMAIN.NAME
dmarc:DOMAIN.NAME:all 

I can see that "two" DKIM - DomainKeys Identified Mail records have also been created in DNS
- my two CNAME records
[ovhmo-selector-1._domainkey        IN CNAME     ovhmo-selector-1._domainkey.XXXXXXX.jt.dkim.mail.ovh.net.]

[ovhmo-selector-2._domainkey        IN CNAME     ovhmo-selector-2._domainkey.XXXXXXX.jt.dkim.mail.ovh.net.]
https://mxtoolbox.com/SuperTool.aspx?action=dkim%3aDOMAIN.NAME%3aovhmo-selector-1&run=toolpage#

SELECTOR1: ovhmo-selector-1
SELECTOR2: ovhmo-selector-2
DOMAIN: DOMAIN.NAME

dkim:DOMAIN.NAME:ovhmo-selector-1
dkim:DOMAIN.NAME:ovhmo-selector-2 

# NSLOOKUP

-------------------------------------------------------
$ nslookup -q=txt ovhmo-selector-1._domainkey.DOMAIN.NAME
;; Truncated, retrying in TCP mode.
Server:        127.0.0.53
Address:    127.0.0.53#53

Non-authoritative answer:
ovhmo-selector-1._domainkey.DOMAIN.NAME    canonical name = ovhmo-selector-1._domainkey.XXXXXXX.jt.dkim.mail.ovh.net.
ovhmo-selector-1._domainkey.XXXXXXX.jt.dkim.mail.ovh.net    text = "v=DKIM1; k=rsa; p=MIIBIjA....Tsymw/wvr2....2Wa0/cymg.....kcG" "b80s/8SYZO...FQxb5h+9mLPN....fEcJ+tm7D....Qffd+K0kb...DAQAB"

-------------------------------------------------------
$  nslookup -q=txt ovhmo-selector-2._domainkey.DOMAIN.NAME
;; Truncated, retrying in TCP mode.
Server:        127.0.0.53
Address:    127.0.0.53#53

Non-authoritative answer:
ovhmo-selector-2._domainkey.DOMAIN.NAME    canonical name = ovhmo-selector-2._domainkey.XXXXXXX.jt.dkim.mail.ovh.net.
ovhmo-selector-2._domainkey.XXXXXXX.jt.dkim.mail.ovh.net    text = "v=DKIM1; k=rsa; p=MIIBIjA....Tsymw/wvr2....2Wa0/cymg.....kcG" "b80s/8SYZO...FQxb5h+9mLPN....fEcJ+tm7D....Qffd+K0kb...DAQAB" 

E-Mails that I send via Zimbra www interface,
are showing on receiving client with a "Warning" in a DKIM Signature:

"Header 'Subject" is not signed"

Is there any way to correct this and
have both Body and Subject signed together?