In some cases you may see this error when inspecting graphs from the check_mssql_health command, but it's currently unknown if this is a general issue or an error that only occurs in some cases.
What has helped in the past that you may want to try is to change the following file:
Modify the line around #266 that looks like this:
$def[$defcnt] .= rrd::line1("bufcahitrat","#000000:");
$def[$defcnt] .= rrd::line1("bufcahitrat","#000000");
Meaning, remove the trailing comma in the second argument.
If you see this error in other templates, it's possible the error is caused by something similar, i.e. too many colons in the rrdtool generated output.
If you are affected by this issue, please contact support. No bug fix has been entered for this issue as it has not been confirmed or reproduced.