With Winter18, elements sizes in compound forms are overridden to something like slds-size--1-of-1, despite the slds-size specified.
For example, this code from the SLDS Documentation used to work, but doesn't work anymore:
<div class="slds-form-compound"> ... <div class="slds-form-element slds-size--1-of-3">
This doesn't work either:
<div class="slds-form-compound"> ... <div class="slds-form-element"> <div class="slds-size--1-of-3">
With Winter18 overrides on our sizes, some elements don't even appear in modals.
Is it a Salesforce bug? Does it happen to you as well? How can we solve?