@Globulopolis hat's a known limitation of the database checker which results in a false alarm. See #36363 . The solution can be found here: #36363 (comment) , i.e. ask them to change their SQL to:

ALTER TABLE `#__jcomments_subscriptions` CHANGE `hash` `hash` CHAR(32) NOT NULL DEFAULT '';
ALTER TABLE `#__jcomments_subscriptions` CHANGE `source` `source` VARCHAR(100) NOT NULL DEFAULT '';

Let me know if this works for you and if they accept that change. If so, I suggest to close this issue.

P.S.: For the long term I'm working on a fix, but in the mean time please ask them to change their update SQL as suggested above,

Thanks for help @richard67
Suggested solution at #36363 (comment) fixed the problem.

@Globulopolis You should also check the comments after the one you have linked, e.g. #36363 (comment) .

I.e. in your case it should be like I suggested above, without the "COLUMN" key word:

ALTER TABLE `#__jcomments_subscriptions` CHANGE `hash` `hash` CHAR(32) NOT NULL DEFAULT '';
ALTER TABLE `#__jcomments_subscriptions` CHANGE `source` `source` VARCHAR(100) NOT NULL DEFAULT '';

@richard67 yes, I split the code and test it. All fine. No errors now.