Can subdomains hurt your primary domain's SEO?

[BHeffernan]

Our primary website https://domain.com has a subdomain https://subDomain.domain.com and on that subdomain we have a jive-hosted community, with a few links to and fro. In GA they are set up as different properties but there are many SEO issues in the jive-hosted site, in which many different people can create content, delete content, comment, etc. There are issues related to how jive structures content, broken links, etc. My question is this: Aside from the SEO issues with the subdomain, can the performance of that subdomain negatively impact the SEO performance and rank of the primary domain? I've heard and read conflicting reports about this and it would be nice to hear from the MOZ community about options to resolve such issues if they exist. Thanks.

[effectdigital]

Under certain circumstances it can harm the rankings and SEO performance of your main site. In terms of low-end technical SEO issues like broken links and stuff, that usually wouldn't be a problem (unless it were creating loads of broken links from the sub-site, to the main site). If you had a more substantial issue like an active penalty (manual GSC notification) or a malware  threat (or hacked content) on your subdomain, that could assuredly harm the main site's rankings. Except in extreme circumstances such as these - I wouldn't worry about it too much

[EGOL]

All of the content that you have on a subdomain and all of the links that the subdomain attracts could have been working to strengthen your root domain.

In Google you are going out to fight the heavyweights.  Do you want to do that with a couple light weight platforms or do you want to unite the clans and attack with all that you got.   That is the choice that you make by running subdomains.

I moved and redirected my subdomains into folders on the main website a long time ago and the results were great.